UCP2 and UCP3 in muscle controlling body metabolism

Gene Expression Profiling of H9c2 Myoblast Differentiation towards a Cardiac-Like Phenotype

H9c2 myoblasts are a cell model used as an alternative for cardiomyocytes. H9c2 cells have the ability to differentiate towards a cardiac phenotype when the media serum is reduced in the presence of all-trans-retinoic acid (RA), creating multinucleated cells with low proliferative capacity. In the present study, we performed for the first time a transcriptional analysis of the H9c2 cell line in two differentiation states, i.e. embryonic cells and differentiated cardiac-like cells. The results show that RA-induced H9c2 differentiation increased the expression of genes encoding for cardiac sarcomeric proteins such as troponin T, or calcium transporters and associated machinery, including SERCA2, ryanodine receptor and phospholamban as well as genes associated with mitochondrial energy production including respiratory chain complexes subunits, mitochondrial creatine kinase, carnitine palmitoyltransferase I and uncoupling proteins. Undifferentiated myoblasts showed increased gene expression of pro-survival proteins such as Bcl-2 as well as cell cycle-regulating proteins. The results indicate that the differentiation of H9c2 cells lead to an increase of transcripts and protein levels involved in calcium handling, glycolytic and mitochondrial metabolism, confirming that H9c2 cell differentiation induced by RA towards a more cardiac-like phenotype involves remodeled mitochondrial function. PI3K, PDK1 and p-CREB also appear to be involved on H9c2 differentiation. Furthermore, complex analysis of differently expressed transcripts revealed significant up-regulation of gene expression related to cardiac muscle contraction, dilated cardiomyopathy and other pathways specific for the cardiac tissue. Metabolic and gene expression remodeling impacts cell responses to different stimuli and determine how these cells are used for biochemical assays.

Current Progress in Sports Genomics

Understanding the genetic architecture of athletic performance is an important step in the development of methods for talent identification in sport. Research concerned with molecular predictors has highlighted a number of potentially important DNA polymorphisms contributing to predisposition to success in certain types of sport. This review summarizes the evidence and mechanistic insights on the associations between DNA polymorphisms and athletic performance. A literature search (period: 1997-2014) revealed that at least 120 genetic markers are linked to elite athlete status (77 endurance-related genetic markers and 43 power/strength-related genetic markers). Notably, 11 (9%) of these genetic markers (endurance markers: ACE I, ACTN3 577X, PPARA rs4253778 G, PPARGC1A Gly482; power/strength markers: ACE D, ACTN3 Arg577, AMPD1 Gln12, HIF1A 582Ser, MTHFR rs1801131 C, NOS3 rs2070744 T, PPARG 12Ala) have shown positive associations with athlete status in three or more studies, and six markers (CREM rs1531550 A, DMD rs939787 T, GALNT13 rs10196189 G, NFIA-AS1 rs1572312 C, RBFOX1 rs7191721 G, TSHR rs7144481 C) were identified after performing genome-wide association studies (GWAS) of African-American, Jamaican, Japanese, and Russian athletes. On the other hand, the significance of 29 (24%) markers was not replicated in at least one study. Future research including multicenter GWAS, whole-genome sequencing, epigenetic, transcriptomic, proteomic, and metabolomic profiling and performing meta-analyses in large cohorts of athletes is needed before these findings can be extended to practice in sport.

Association of UCP-3 rs1626521 with obesity and stomach functions in humans

OBJECTIVE

To examine the association of gene variants of uncoupling proteins (UCP)-2 and -3 with obesity and gastrointestinal (GI) traits.

METHODS

In 255 overweight or obese adults, the associations of gene variants in UCP-2 (-3474, rs659366) and UCP-3 (rs1626521, rs2075577, rs15763) with body weight (BW) and GI traits were studied. Gene variants were genotyped by TaqMan® assay. The associations of genotypes with BW and GI traits (gastric emptying, gastric volume, satiety by buffet meal, satiation by nutrient drink test and GI hormones) were assessed using ANOVA corrected for false detection rate (FDR).

RESULTS

A novel UCP-3 gene variant, rs1626521, was identified; it was associated with BW (P = 0.039), waist circumference (P = 0.035), and significantly higher postprandial gastric volume (P = 0.003) and calories ingested at buffet meal (P = 0.006, both significant with FDR). In a subgroup of 11 participants, rs1626521 was also associated with reduced mitochondrial bioenergetics efficiency in skeletal muscle (P = 0.051). In an in vitro study in HEK293 cells, rs1626521 reduced UCP-3 protein expression (P = 0.049). Associations detected between other genotypes and GI traits were nonsignificant with FDR.

CONCLUSIONS

A newly identified functional variant (rs1626521) in UCP-3 affects postprandial gastric functions and satiety and may contribute to weight gain and alter human mitochondrial function.

Relationship between expression of muscle-specific uncoupling protein 2 messenger RNA and genetic selection toward growth in channel catfish

This study tested the hypothesis that increased growth in channel catfish is associated with expression of the genes that code for uncoupling proteins (UCP) 2 and 3, members of the mitochondrial channel proteins involved in nutrient sensing and metabolism. The specific objective was to contrast the levels of UCP2 messenger RNA (mRNA) in fast vs slow growing catfish as well as in fed vs fasted catfish. Two distinct UCP2 transcripts were identified and named UCP2a and UCP2b, respectively. Nucleotide and amino acid sequence of catfish UCP2s were highly similar to UCP2 and other UCPs from other fish and mammals (>75%). Expression of UCP2a mRNA was detectable at very low levels in various metabolically active tissues, whereas the expression of UCP2b mRNA was readily detectable in the muscle and heart. In a 21-wk feeding study, fish that grew faster had a greater percent body fat at the end of the study (P < 0.01). Expression of UCP2b mRNA tended to be lower (P < 0.10) in fast growing fish in the middle of the study although levels were similar at the beginning and the end of the study. In the fed vs fasted study, expression of UCP2b mRNA in muscle was increased (P < 0.05) in fish assigned to 30 d of fasting. Our results suggest that, based on the nucleotide and amino acid sequence similarities and tissue mRNA distribution, catfish UCP2b may be the analog to UCP3. Moreover, our results suggest selection toward growth and associated fat accumulation appears to be independent of muscle UCP2b mRNA expression and UCP2b-mediated mechanisms.

Beneficial role of bitter melon supplementation in obesity and related complications in metabolic syndrome

Diabetes, obesity, and metabolic syndrome are becoming epidemic both in developed and developing countries in recent years. Complementary and alternative medicines have been used since ancient era for the treatment of diabetes and cardiovascular diseases. Bitter melon is widely used as vegetables in daily food in Bangladesh and several other countries in Asia. The fruits extract of bitter melon showed strong antioxidant and hypoglycemic activities in experimental condition both in vivo and in vitro. Recent scientific evaluation of this plant extracts also showed potential therapeutic benefit in diabetes and obesity related metabolic dysfunction in experimental animals and clinical studies. These beneficial effects are mediated probably by inducing lipid and fat metabolizing gene expression and increasing the function of AMPK and PPARs, and so forth. This review will thus focus on the recent findings on beneficial effect of Momordica charantia extracts on metabolic syndrome and discuss its potential mechanism of actions.

Perspectives on mitochondrial uncoupling proteins-mediated neuroprotection

The integrity of mitochondrial function is essential to cell life. It follows that disturbances of mitochondrial function will lead to disruption of cell function, expressed as disease or even death. Considering that neuronal uncoupling proteins (UCPs) decrease reactive oxygen species (ROS) production at the expense of energy production, it is important to understand the underlying mechanisms by which UCPs control the balance between the production of adenosine triphosphate (ATP) and ROS in the context of normal physiological activity and in pathological conditions. Here we review the current understanding of neuronal UCPs-mediated respiratory uncoupling process by performing a survey in their physiology and regulation. The latest findings regarding neuronal UCPs physiological roles and their involvement and interest as potential targets for therapeutic intervention in brain diseases will also be exploited.

Corn gluten hydrolysate and capsaicin have complimentary actions on body weight reduction and lipid-related genes in diet-induced obese rats

The aim of this study was to test the hypothesis that a combination of corn gluten hydrolysate (CGH) and capsaicin may have an additive or synergistic effect on body weight reduction. For 13 weeks, male Sprague-Dawley rats were provided a diet to induce obesity. Afterward, the rats were randomly divided into 5 dietary groups: the normal control (n = 5), the high-fat control (n = 8), the high-fat diet (HFD) containing 35% CGH (n = 7), the HFD containing 0.02% capsaicin (HF-P) (n = 8), and the HFD containing both CGH and capsaicin (HF-CP) (n = 7) for an additional 4 weeks. Administration of CGH plus capsaicin, along with a HFD, led to significant decreases in body weight, fat mass, lipids in the liver, and plasma leptin as well as increases in plasma adiponectin. The pattern of gene expression was different in each target organ. In the liver, up-regulation of peroxisome proliferator-activated receptor α, carnitine palmitoyltransferase 1α, and acyl-coenzyme A oxidase was found in the HF-CP group. In contrast, down-regulation of peroxisome proliferator-activated receptor γ was found in both the HFD containing 35% CGH and HF-CP groups. In skeletal muscle, up-regulation of insulin receptor and uncoupling protein 3 was found in the HF-P group only, whereas up-regulation of the glucose transporter 4 gene was observed in both the HF-CP and HF-P groups. In adipose tissue, up-regulation of peroxisome proliferator-activated receptor γ and hormone-sensitive lipase was only found in the HF-CP group. In summary, this study suggests that CGH and capsaicin perform complementary actions on food intake, lipid metabolism, and insulin sensitivity by a coordinated control of energy metabolism in the liver, adipose tissue, and skeletal muscle, thus exerting an additive effect on body weight reduction.

Low serum concentrations of carotenoids and vitamin E are associated with high adiposity in Mexican-American children

Mexican-American children have a high prevalence of overweight/obesity. Micronutrient deficiencies may be contributing to the development of greater adiposity in these children. This study investigated the relations between adiposity and serum concentrations of carotenoids, retinol, and vitamin E among Mexican-American children 8-15 y of age included in the 2001-2004 U.S. NHANES. Associations of the outcomes of children's body mass index (BMI), truncal fat mass (TrFM), and total body fat mass (TBFM) with serum concentrations of α-carotene, cis-β-carotene, trans-β-carotene, retinol, and α-tocopherol were determined by using linear, quantile, and multinomial regression models. BMI was inversely associated with serum concentrations of α-carotene (β = -0.88, P < 0.05), trans-β-carotene (β = -2.21, P < 0.01), cis-β-carotene (β = -2.10, P < 0.01), and α-tocopherol adjusted for total cholesterol ratio (β = -3.66, P < 0.01), respectively. Similar inverse associations were found with TrFM and TBFM. Higher cis-β-carotene and α-tocopherol serum concentrations were associated with reduced probability of overweight (OR: 0.57; 95% CI: 0.37, 0.89; P < 0.05; and OR: 0.56; 95% CI: 0.37, 0.86; P < 0.05; respectively) and obesity (OR: 0.39; 95% CI: 0.26, 0.58; P < 0.01; and OR: 0.38; 95% CI: 0.24, 0.60; P < 0.01; respectively). Higher retinol serum concentrations were associated with increased probability of overweight and obesity (OR: 2.01; 95% CI: 1.26, 3.22; P < 0.01; and OR: 2.90; 95% CI: 1.65, 5.09; P < 0.01; respectively). Significant inverse associations were found between serum concentrations of carotenoids and vitamin E and adiposity among Mexican-American children, but serum retinol concentrations were positively associated with adiposity. Future research is needed to understand the causes and consequences of micronutrient status on adiposity and comorbidities.

Association of genetic variants of ghrelin, leptin and UCP2 with malnutrition inflammation syndrome and survival in end-stage renal disease patients

Malnutrition inflammation syndrome (MIS) is common among ESRD patients. In the present study, we have investigated the association of genetic markers associated with appetite and energy regulation with malnutrition inflammation syndrome among end-stage renal disease (ESRD) patients. Two hundred and fifty-seven patients on maintenance hemodialysis and 200 normal healthy controls were included in the study. Nutritional assessment was done by subjective global assessment scores (SGA). Genotyping of leptin-2548 G/A (rs7799039), ghrelin Leu72Met (rs696217-408 C/A), Arg51Gln (rs34911341-346 G/A) and uncoupling protein 2 (UCP2) 45 bp insertion deletion was done using PCR-RFLP. Levels of leptin and acyl ghrelin were assessed using ELISA. Leptin-2548 AA genotype was associated with twofold higher risk of disease susceptibility while UCP2 insertion-deletion heterozygotes showed protective effect. Ghrelin Gln51Gln and Met72Met genotype were associated with 3.4- and 2.5-fold higher disease susceptibility. The Met72 and Gln51 allele showed 3.3- and 2.1-fold higher susceptibility to malnutrition in severe SGA group. Further, the levels of acyl ghrelin were significantly less in severe category of malnutrition and in poor appetite group. On combined analysis, the group 2 (presence of 3-4 risk alleles) showed 1.5- and twofold higher susceptibility to disease and malnutrition, respectively. On docking analysis, it was observed that higher receptor binding energy was associated with the mutant form of ghrelin (Gln51). Moderate and severe SGA were associated with 2.2- and 4.1-fold higher death hazard. Our study suggests that ghrelin may be major marker contributing to susceptibility to MIS among ESRD patients.

Endurance training blocks uncoupling protein 1 up-regulation in brown adipose tissue while increasing uncoupling protein 3 in the muscle tissue of rats fed with a high-sugar diet

The mitochondrial uncoupling proteins (UCPs) of interscapular brown adipose tissue (iBAT) and of muscles play important roles in energy balance. For instance, the expression of UCP1 and UCP3 are modulated by free fatty acid gradients induced by high-sugar diets and acute exercise that is dependent on sympathetic stimulation. However, the effects of endurance training in animals fed with high-sugar diets are unknown. This study aims to evaluate the long-term effects of diet and exercise on UCP1 and UCP3 levels and energy balance efficiency. Rats fed with standard or high-sugar (HSD) diets were simultaneously subjected to running training over an 8-week period. After the training period, the rats were decapitated, and the iBAT and gastrocnemius muscle tissues were removed for evaluation of the β₃-receptor, Ucp1, and Ucp3 mRNA and protein expression, which were analyzed by quantitative reverse transcriptase polymerase chain reaction and Western blot, respectively. Groups fed with an HSD displayed a higher adiposity index and iBAT weight (P < .05), whereas exhibited an up-regulation of Ucp1 mRNA and protein levels (P < .05). Training increased β₃-receptor mRNA in iBAT and reduced the Ucp3 mRNA in muscle tissues. In association with an HSD, training restored the increasing β₃-receptor mRNA and greatly up-regulated the levels of Ucp3 mRNA. Therefore, training blocked the HSD-induced up-regulation of UCP1 expression in iBAT, whereas it up-regulated the expression of Ucp3 mRNA in muscle. These results suggest that training enhances the relationship between Ucp1/Ucp3 mRNA levels, which could result in higher energy efficiency, but not when HSD-induced elevated sympathetic activity is maintained.

Human Uncoupling Protein-3 and Obesity: An Update

The cloning of the uncoupling protein (UCP)1 homologs UCP2 and UCP3 has raised considerable interest in the mechanism. The expression of UCP3 mainly in skeletal muscle mitochondria and the potency of the skeletal muscle as a thermogenic organ made UCP3 an attractive target for studies toward manipulation of energy expenditure to fight disorders such as obesity and type 2 diabetes. Overexpressing UCP3 in mice resulted in lean, hyperphagic mice. However, the lack of an apparent phenotype in mice lacking UCP3 triggered the search for alternative functions of UCP3. The observation that fatty acid levels significantly affect UCP3 expression has given UCP3 a position in fatty acid handling and/or oxidation. Emerging data indicate that the primary physiological role of UCP3 may be the mitochondrial handling of fatty acids rather than the regulation of energy expenditure through thermogenesis. It has been proposed that UCP3 functions to export fatty acid anions away from the mitochondrial matrix. In doing so, fatty acids are exchanged with protons, explaining the uncoupling activity of UCP3. The exported fatty acid anions may originate from hydrolysis of fatty acid esters by a mitochondrial thioesterase, or they may have entered the mitochondria as nonesterified fatty acids by incorporating into and flip-flopping across the mitochondrial inner membrane. Regardless of the origin of the fatty acid anions, this putative function of UCP3 might be of great importance in protecting mitochondria against fatty acid accumulation and may help to maintain muscular fat oxidative capacity.

Central administration of aminoprocalcitonin inhibits food intake and stimulates the hypothalamic-pituitary-adrenal axis in rats via the corticotrophin-releasing factor system

Aminoprocalcitonin (N-PCT), a neuroendocrine peptide derived from procalcitonin, reduces food intake and body weight when administered centrally in rats. We have recently shown that N-PCT is expressed in brain areas known to be involved in energy homeostasis, including the paraventricular nucleus (PVN) of the hypothalamus, which contains a prominent population of corticotrophin-releasing factor (CRF)-synthesising neurones. CRF plays a pivotal role in the regulation of the hypothalamic-pituitary adrenal (HPA) axis and food intake. However, little is known about functional interactions of N-PCT and CRF. In the present study, we found endogenous N-PCT protein in the rat PVN. We also showed N-PCT immunoreactivity in PVN co-localised with NeuN, a neuronal marker, or glial fibrillary acidic protein, an astrocyte marker. Double staining immunohistochemistry revealed that N-PCT co-localised with CRF in parvocellular neurones of the PVN. Intracerebroventricular N-PCT administration increased CRF mRNA and content in the hypothalamus, suggesting that N-PCT stimulates the HPA axis and suppresses food intake and body weight via CRF-dependent pathways. In keeping with this, i.c.v. co-injection of D-Phe-CRF(12-41), a CRF receptor antagonist, significantly attenuated N-PCT-induced reduction in food intake and body weight in a dose-dependent manner. Furthermore, i.c.v. administration of N-PCT increased plasma adrenocorticotrophic hormone and corticosterone concentrations and induced the expression of Fos protein, a marker of neuronal activity, in parvocellular CRF neurones. These data collectively support the hypothesis that N-PCT inhibits food intake and body weight and stimulates the HPA axis via CRF-mediated pathways.

Metabolic programming of sirtuin 1 (SIRT1) expression by moderate energy restriction during gestation in rats may be related to obesity susceptibility in later life

In rats, 20% gestational energy restriction programmes offspring for higher food intake, which in adulthood results in higher body weight in males but not in females. Here, we aimed to assess whether the effects of moderate energy restriction during gestation and the sex-related outcomes on adult body weight may be related to the metabolic programming of sirtuin expression in different tissues. For this purpose, 25-d-old offspring of control and 20% energy-restricted (ER) rats (from days 1-12 of pregnancy) were studied. Body weight and the weight of white adipose tissue (WAT) depots and liver were recorded and mRNA expression of sirtuin 1 (SIRT1) and selected genes in the WAT, liver, muscle and hypothalamus were analysed. No differences were found in body weight or the weight of WAT and liver between the control and ER animals. A similar pattern of SIRT1 mRNA expression was found in the WAT, liver and skeletal muscle of ER animals, but in a sex-dependent manner: ER males showed lower SIRT1 mRNA levels than the controls, while no differences were found in females. A sex-different pattern was also observed in the hypothalamus. ER males, but not females, also showed lower mRNA levels of adipose TAG lipase (ATGL) and uncoupling protein 2 in WAT and of sterol response element binding protein 1c and stearoyl-CoA desaturase-1 in the liver. Both sexes of ER animals showed lower mRNA levels of 5' adenosine monophosphate-activated protein kinase and ATGL in the liver. In conclusion, moderate maternal energy restriction during gestation programmes a particular, sex-dependent gene expression profile of SIRT1 in different peripheral tissues, which may be related to obesity predisposition in adulthood; therefore SIRT1 expression emerges as a potential early biomarker of obesity susceptibility.

Uncoupling protein-2 45-base pair insertion/deletion polymorphism: is there an association with severe obesity and weight loss in morbidly obese subjects?

BACKGROUND

Uncoupling proteins are attractive candidate genes for obesity and type 2 diabetes mellitus. Our aim was to investigate the potential association of the uncoupling protein-2 (UCP2) 45-bp insertion/deletion (ins/del) polymorphism with obesity, as well as the potential effect of this polymorphism on weight loss variability in severely obese subjects.

METHODS

A total of 158 severely obese subjects (94 without and 64 with metabolic syndrome) and 91 age and sex-matched lean controls were recruited. A subgroup of 124 obese patients participated in a 3-month weight loss program. Anthropometric and metabolic variables were measured. Participants were genotyped for the UCP2 ins/del polymorphism.

RESULTS

Allelic frequency differed neither between obese subjects and controls (P=0.56), nor between obese subjects with versus without metabolic syndrome (P=0.58). At 3 months, metabolically healthy subjects carrying the insertion allele had significantly greater reduction in body mass index (P=0.029) and fat-free mass (P=0.013) and a borderline significant improvement in the homeostatic model assessment index (P=0.048).

CONCLUSION

There is no association of the UCP2 ins/del polymorphism with morbid obesity in our population, but this genotype appears to be linked with a favorable response to dietary changes in metabolically healthy obese subjects.

TRPV1 activation prevents nonalcoholic fatty liver through UCP2 upregulation in mice

Nonalcoholic fatty liver is characterized by the fatty deformation and lipid deposition of hepatic parenchymal cells that are associated with cardiometabolic diseases. In this study, we report the effect of capsaicin on its receptor, transient receptor potential vanilloid 1 (TRPV1) cation channel, in preventing fatty liver formation. Functional TRPV1 has been detected in hepatocytes and liver tissues. TRPV1 activation by capsaicin reduced lipid accumulation and triglyceride level in the liver from wild-type (WT) mice. However, these effects were absent in the liver from TRPV1(-/-) mice. Chronic dietary capsaicin increased the hepatic uncoupling protein 2 (UCP2) expression in WT but not in TRPV1(-/-) mice (P < 0.01). We conclude that TRPV1 long-time activation might prevent high-fat diet-induced fatty liver in mice through upregulation of hepatic UCP2. Dietary capsaicin may represent a promising intervention in populations at high risk for fatty liver.

A/ASP/VAL allele combination of IGF1R, IRS2, and UCP2 genes is associated with better metabolic profile, preserved energy expenditure parameters, and low mortality rate in longevity

A large array of gene involved in human longevity seems to be in relationship with insulin/IGF1 pathway. However, if such genes interact each other, or with other genes, to reduce the age-related metabolic derangement and determine the long-lived phenotype has been poorly investigated. Thus, we tested the role of interchromosomal interactions among IGF1R, IRS2, and UCP2 genes on the probability to reach extreme old age in 722 unrelated Italian subjects (401 women and 321 men; mean age, 62.83 ± 25.30 years) enrolled between 1998 and 1999. In particular, the G/A-IGF1R, Gly/Asp-IRS2, and Ala/Val-UCP2 allele combination was tested for association with longevity, metabolic profile and energy expenditure parameters. The effect on all-cause and cause-specific mortality rate was also assessed after a mean follow-up of 6 years. The analysis revealed that AAV allele combination is associated with a decreased all-cause mortality risk (HR, 0.72; 95% CI, 0.63-0.91; p = 0.03) and with a higher probability to reach the extreme of old age (OR, 3.185; 95% CI, 1.63-6.19; p = 0.0006). The analysis also revealed lower HOMA-IR (Diff, -0.532, 95% CI, 0.886-0.17; p = 0.003), higher respiratory quotient (Diff, 0.0363, 95% CI, 0.014-0.05; p = 0.001), and resting metabolic rate (Diff, 101.80693, 95% CI, -5.26-204.278; p = 0.038) for AAV allele combination. In conclusion, A-IGF1R/Asp-IRS2/Val-UCP2 allele combination is associated with a decreased all-cause mortality risk and with an increased chance of longevity. Such an effect is probably due to the combined effect of IGF1R, IRS2, and UCP2 genes on energy metabolism and on the age-related metabolic remodeling capacity.

Central leptin activates mitochondrial function and increases heat production in skeletal muscle

Leptin acts on the brain to increase postprandial heat production in skeletal muscle of sheep. To determine a mechanism for this effect, we examined the role of mitochondrial uncoupling and AMP-activated protein kinase (AMPK). Ovariectomized ewes (n=4/group) received infusion lines into the lateral cerebral ventricle, and leptin (10 μg/h) was infused to increase heat production in skeletal muscle. In animals that were program fed (1100-1600 h), skeletal muscle biopsies were taken after either central infusion of leptin or vehicle to measure the expression of uncoupling protein (UCP) mRNA and the phosphorylation status of AMPK. Respiratory function was also quantified in mitochondria isolated from skeletal muscle. Leptin infusion increased the expression of UCP2 and UCP3 mRNA as well as UCP3 protein but not UCP1 mRNA in muscle. Leptin also increased substrate-driven, coupled (ADP-driven), and uncoupled (oligomycin) respiration but had no effect on the total respiratory capacity. The respiratory control ratio was lower in leptin-treated (vs. vehicle-treated) animals, indicating a predominant effect on uncoupled respiration. There was no effect of central leptin treatment on AMPK phosphorylation. We then infused 5-aminoimidazole-4-carboxamide-1β-riboside (AICAR) (10 mg/h for 6 h) directly into the femoral artery and measured skeletal muscle temperature; muscle was also collected for isolated mitochondria studies. AICAR had no effect on heat production or substrate-driven, uncoupled, or total respiratory states in skeletal muscle mitochondria. However, AICAR increased ADP-driven (coupled) respiration in mitochondria. In conclusion, leptin acts at the brain to increase heat production in muscle through altered mitochondrial function, indicative of adaptive thermogenesis.

Changes in expression of skeletal muscle proteins between obesity-prone and obesity-resistant rats induced by a high-fat diet

A primary goal in obesity research is to determine why some people become obese (obesity-prone, OP) and others do not (obesity-resistant, OR) when exposed to high-calorie diets. The metabolic changes that cause reduced adiposity and resistance to obesity development have yet to be determined. We thus performed proteomic analysis on muscular proteins from OP and OR rats in order to determine whether other novel molecules are involved in this response. To this end, rats were fed a low- or high-fat diet for 8 weeks and were then classified into OP and OR rats by body weight gain. OP rats gained about 25% more body weight than OR rats, even though food intake did not differ significantly between the two groups. Proteomic analysis using 2-DE demonstrated differential expression of 26 spots from a total of 658 matched spots, of which 23 spots were identified as skeletal muscle proteins altered between OP and OR rats by peptide mass fingerprinting. Muscle proteome data enabled us to draw the conclusion that enhanced regulation of proteins involved in lipid metabolism and muscle contraction, as well as increased expression of marker proteins for oxidative muscle type (type I), contributed to obesity-resistance; however, antioxidative proteins did not.

The transcriptional coregulators TIF2 and SRC-1 regulate energy homeostasis by modulating mitochondrial respiration in skeletal muscles

The two p160 transcriptional coregulator family members SRC-1 and TIF2 have important metabolic functions in white and brown adipose tissues as well as in the liver. To analyze TIF2 cell-autonomous functions in skeletal muscles, we generated TIF2((i)skm)⁻(/)⁻ mice in which TIF2 was selectively ablated in skeletal muscle myofibers at adulthood. We found that increased mitochondrial uncoupling in skeletal muscle myocytes protected these mice from decreased muscle oxidative capacities induced by sedentariness, delayed the development of type 2 diabetes, and attenuated high-caloric-diet-induced obesity. Moreover, our results demonstrate that SRC-1 and TIF2 can modulate the expression of the uncoupling protein 3 (UCP3) in an antagonistic manner and that enhanced SRC-1 levels in TIF2-deficient myofibers are critically involved in the metabolic changes of TIF2((i)skm)⁻(/)⁻ mice. Thus, modulation of the expression and/or activity of these coregulators represents an attractive way to prevent or treat metabolic disorders.

Effects of multivitamin and mineral supplementation on adiposity, energy expenditure and lipid profiles in obese Chinese women

BACKGROUND

Obese individuals are more likely to have either lower blood concentrations or lower bioavailability of minerals and/or vitamins. However, there are limited data on the effects of nutritional supplementation on body weight (BW) control, energy homeostasis and lipid metabolism in obese subjects.

OBJECTIVE

The purpose of this study is to evaluate the effects of supplementation with multivitamin and multimineral on adiposity, energy expenditure and lipid profiles in obese Chinese women.

DESIGN

A total of 96 obese Chinese women (body mass index (BMI) 28 kg m(-2)) aged 18-55 years participated in a 26-week randomized, double-blind, placebo-controlled intervention study. Subjects were randomized into three groups, receiving either one tablet of multivitamin and mineral supplement (MMS), or calcium 162 mg (Calcium) or identical placebo daily during the study period. BW, BMI, waist circumference (WC), fat mass (FM), fat-free mass, resting energy expenditure (REE), respiratory quotient (RQ), blood pressure, fasting plasma glucose and serum insulin, total cholesterol (TC), low- and high-density lipoprotein-cholesterol (LDL-C and HDL-C) and triglycerides (TGs) were measured at baseline and 26 weeks.

RESULTS

A total of 87 subjects completed the study. After 26 weeks, compared with the placebo group, the MMS group had significantly lower BW, BMI, FM, TC and LDL-C, significantly higher REE and HDL-C, as well as a borderline significant trend of lower RQ (P=0.053) and WC (P=0.071). The calcium group also had significantly higher HDL-C and lower LDL-C levels compared with the placebo group.

CONCLUSION

The results suggest that, in obese individuals, multivitamin and mineral supplementation could reduce BW and fatness and improve serum lipid profiles, possibly through increased energy expenditure and fat oxidation. Supplementation of calcium alone (162 mg per day) only improved lipid profiles.

Variation in the UCP2 and UCP3 genes associates with abdominal obesity and serum lipids: the Finnish Diabetes Prevention Study

Background

We explored the associations of three variants in the uncoupling protein 2 (UCP2) gene, one variant in the UCP2-UCP3 intergenic region and five variants in the uncoupling protein 3 (UCP3) gene with obesity and diabetes related traits in subjects with impaired glucose tolerance participating in Finnish Diabetes Prevention Study. Altogether 507 overweight individuals (body mass index: 31.2 ± 4.5 kg/m², age: 55 ± 7 years) for whom DNA was available were randomized to either an intensified diet and physical activity group or to a conventional care control group.

Methods

We analysed the data from the baseline and annual follow-up visits from years 1, 2 and 3. Measurements of anthropometry, plasma glucose and serum insulin in oral glucose tolerance test, serum total cholesterol, HDL-cholesterol and triglycerides were included. The median follow-up time for type 2 diabetes incidence was 7 years. Genetic variants were screened by restriction fragment length polymorphism or Illumina method.

Results

UCP3 gene variant rs3781907 was associated with increased serum total and LDL-cholesterol levels, at baseline and during the follow-up period. The same variant was associated with a higher risk of type 2 diabetes. Variants rs1726745, rs11235972 and rs1800849 in the UCP3 gene associated with serum total and LDL-cholesterol at baseline. Haploblock including variants rs659366, rs653529, rs15763, and rs1726745 was associated with measures of abdominal obesity at baseline and in the longitudinal analysis. The haplotype comprising alleles rs659366-G, rs653529-A, rs15763-G and rs1726745-A was associated with higher waist-to-hip ratio, and haplotype comprising alleles rs3781907-G, rs11235972-A, and rs1800849-T was associated with increased serum total and LDL-cholesterol concentrations.

Conclusion

Genetic variation in the UCP2-UCP3 gene cluster may act as a modifier increasing serum lipid levels and indices of abdominal obesity, and may thereby also contribute to the metabolic aberrations observed in obesity and type 2 diabetes.

Genetic variation in healthy oldest-old

Individuals who live to 85 and beyond without developing major age-related diseases may achieve this, in part, by lacking disease susceptibility factors, or by possessing resistance factors that enhance their ability to avoid disease and prolong lifespan. Healthy aging is a complex phenotype likely to be affected by both genetic and environmental factors. We sequenced 24 candidate healthy aging genes in DNA samples from 47 healthy individuals aged eighty-five years or older (the 'oldest-old'), to characterize genetic variation that is present in this exceptional group. These healthy seniors were never diagnosed with cancer, cardiovascular disease, pulmonary disease, diabetes, or Alzheimer disease. We re-sequenced all exons, intron-exon boundaries and selected conserved non-coding sequences of candidate genes involved in aging-related processes, including dietary restriction (PPARG, PPARGC1A, SIRT1, SIRT3, UCP2, UCP3), metabolism (IGF1R, APOB, SCD), autophagy (BECN1, FRAP1), stem cell activation (NOTCH1, DLL1), tumor suppression (TP53, CDKN2A, ING1), DNA methylation (TRDMT1, DNMT3A, DNMT3B) Progeria syndromes (LMNA, ZMPSTE24, KL) and stress response (CRYAB, HSPB2). We detected 935 variants, including 848 single nucleotide polymorphisms (SNPs) and 87 insertion or deletions; 41% (385) were not recorded in dbSNP. This study is the first to present a comprehensive analysis of genetic variation in aging-related candidate genes in healthy oldest-old. These variants and especially our novel polymorphisms are valuable resources to test for genetic association in models of disease susceptibility or resistance. In addition, we propose an innovative tagSNP selection strategy that combines variants identified through gene re-sequencing- and HapMap-derived SNPs.

Adenylate kinase and AMP signaling networks: metabolic monitoring, signal communication and body energy sensing

Adenylate kinase and downstream AMP signaling is an integrated metabolic monitoring system which reads the cellular energy state in order to tune and report signals to metabolic sensors. A network of adenylate kinase isoforms (AK1-AK7) are distributed throughout intracellular compartments, interstitial space and body fluids to regulate energetic and metabolic signaling circuits, securing efficient cell energy economy, signal communication and stress response. The dynamics of adenylate kinase-catalyzed phosphotransfer regulates multiple intracellular and extracellular energy-dependent and nucleotide signaling processes, including excitation-contraction coupling, hormone secretion, cell and ciliary motility, nuclear transport, energetics of cell cycle, DNA synthesis and repair, and developmental programming. Metabolomic analyses indicate that cellular, interstitial and blood AMP levels are potential metabolic signals associated with vital functions including body energy sensing, sleep, hibernation and food intake. Either low or excess AMP signaling has been linked to human disease such as diabetes, obesity and hypertrophic cardiomyopathy. Recent studies indicate that derangements in adenylate kinase-mediated energetic signaling due to mutations in AK1, AK2 or AK7 isoforms are associated with hemolytic anemia, reticular dysgenesis and ciliary dyskinesia. Moreover, hormonal, food and antidiabetic drug actions are frequently coupled to alterations of cellular AMP levels and associated signaling. Thus, by monitoring energy state and generating and distributing AMP metabolic signals adenylate kinase represents a unique hub within the cellular homeostatic network.

In vitro evidence suggests that miR-133a-mediated regulation of uncoupling protein 2 (UCP2) is an indispensable step in myogenic differentiation

UCP2 and UCP3, two novel uncoupling proteins, are important regulators of energy expenditure and thermogenesis in various organisms. The striking disparity between UCP2 mRNA and protein levels in muscle tissues prompted initial speculation that microRNAs are implicated in the regulatory pathway of UCP2. We found, for the first time, that the repression of UCP2 expression in cardiac and skeletal muscle resulted from its targeting by a muscle-specific microRNA, miR-133a. Moreover, our findings illustrate a novel function of UCP2 as a brake for muscle development. We also show that MyoD can remove the braking role of UCP2 via direct up-regulation of miR-133a during myogenic differentiation. Taken together, our current work delineates a novel regulatory network employing MyoD, microRNA, and uncoupling proteins to fine-tune the balance between muscle differentiation and proliferation during myogenesis.

Energetics of fasting heterothermia in TRPV1-KO and wild type mice

To learn the possible role of TRPV1 in the changes of temperature regulation induced by short-term energy lack, TRPV1-KO and wild type mice were exposed to complete fasting for 2 or 3 days while their core temperature and locomotor activity were recorded using a biotelemetry method. In both types of mice, fasting led to progressive daytime hypothermia with night-time core temperature being maintained at normothermia (collectively called heterothermia). During fasting rises of locomotor activity were observed parallel to night-time normothermia with occasional increases of both parameters recorded every 2 to 3 hours (ultradian rhythms). The daytime fall of core temperature was significantly greater in wild type than in TRPV1-KO mice, in the former an advance of the temperature/activity rhythm having been observed in spite of the presence of a 12/12 hour light/darkness schedule. Re-feeding applied at the beginning of the light-period led to rapid reappearance of normothermia in both types of mice without a large increase in locomotor activity. It is concluded that the TRPV1-gene may have a role in the development of adaptive daytime hypothermia (and hence saving some energy) in mice during complete fasting but still allowing normothermia maintained at night, a strategy probably serving survival under natural conditions in small size rodents such as the mouse. The possible role of muscle thermogenesis either with or without gross bodily movement during fasting or on re-feeding, respectively, may be based on different mechanisms yet to be clarified.

Recent developments in calcium-related obesity research

The influence of calcium and dairy food intake on energy balance is the object of a growing scientific literature. This manuscript presents the information discussed by subject experts during a symposium on calcium and obesity, initially planned to document in a comprehensive manner the role of calcium and dairy food on energy balance and body composition. This manuscript is organized into 13 propositions statements which either resume the presentation of an invited speaker or integrate recent developments in calcium-related obesity research. More specifically, the effects of calcium and dairy consumption on body weight and adiposity level, appetite, weight loss intervention outcome, lipid-lipoprotein profile and the risk to develop metabolic syndrome are discussed together with the metabolic mechanisms proposed to explain these effects. Taken together, the observations presented in this manuscript suggest that calcium and dairy food intake can influence many components of energy and fat balance, indicating that inadequate calcium/dairy intake may increase the risk of positive energy balance and of other health problems.

Profiling postprandial thermogenesis in muscle and fat of sheep and the central effect of leptin administration

Brown adipose tissue thermogenesis is an important component of energy expenditure as exemplified in rodents. Other tissues such as white adipose tissue and muscle are also capable of thermogenesis, but regulation of heat production in these tissues is poorly understood. We used a relatively large animal model, the ovariectomized sheep, in which site-specific temperature measurements were made as an index of thermogenic output. Dataloggers were implanted into the retroperitoneal (visceral) fat, gluteal (sc) fat, and skeletal muscle of the hind limb, and were programmed to record temperature every 15 min. Animals (n = 4) were then placed on a feeding schedule (fed between 1100 and 1600 h) to entrain a postprandial response in thermogenesis. Baseline thermogenesis (0800-1100 h) was higher (P < 0.05) in visceral fat and muscle than in gluteal fat, whereas the amplitude of the postprandial increase was similar at all three sites. Intracerebroventricular infusion into the lateral ventricle of either vehicle (artificial cerebrospinal fluid) or leptin (10 microg/h at 100 microl/h) for 24 h (0900-0900) was performed in a cross-over design with a 1-wk recovery period between treatments. Central leptin infusion did not alter the basal thermogenic rate but markedly enhanced the postprandial response in both fat and muscle tissues. This was manifest by increased (P < 0.05) amplitude and duration of the postprandial thermogenic response, and the effect was greater in muscle and visceral fat than in gluteal fat. These data demonstrate that leptin is able to regulate thermogenesis in muscle, providing a novel target for the manipulation of energy balance.

Increased thermoregulation in cold-exposed transgenic mice overexpressing lipoprotein lipase in skeletal muscle: an avian phenotype?

LPL is an enzyme involved in the breakdown and uptake of lipoprotein triglycerides. In the present study, we examined how the transgenic (Tg) overexpression of human LPL in mouse skeletal muscle affected tolerance to cold temperatures, cold-induced thermogenesis, and fuel utilization during this response. Tg mice and their nontransgenic controls were placed in an environmental chamber and housed in metabolic chambers that monitored oxygen consumption and carbon dioxide production with calorimetry. When exposed to 4 degrees C, an attenuation in the decline in body temperature in Tg mice was accompanied by an increased metabolic rate (15%; P < 0.001) and a reduction in respiratory quotient (P < 0.05). Activity levels, the expression of uncoupling proteins in brown fat and muscle, and lean mass failed to explain the enhanced cold tolerance and thermogenesis in Tg mice. The more oxidative type IIa fibers were favored over the more glycolytic type IIb fibers (P < 0.001) in the gastrocnemius and quadriceps muscles of Tg mice. These data suggest that Tg overexpression of LPL in skeletal muscle increases cold tolerance by enhancing the capacity for fat oxidation, producing an avian-like phenotype in which skeletal muscle contributes significantly to the thermogenic response to cold temperatures.

Mitochondrial medicine: pharmacological targeting of mitochondria in disease

Mitochondria play a central role in cell life and death and are known to be important in a wide range of diseases including the cancer, diabetes, cardiovascular disease, and the age-related neurodegenerative diseases. The unique structural and functional characteristics of mitochondria enable the selective targeting of drugs designed to modulate the function of this organelle for therapeutic gain. This review discusses mitochondrial drug targeting strategies and a variety of novel mitochondrial drug targets including the electron transport chain, mitochondrial permeability transition, Bcl-2 family proteins and mitochondrial DNA. Mitochondrial drug-targeting strategies will open up avenues for manipulating mitochondrial functions and allow for selective protection or eradication of cells for therapeutic gain in a variety of diseases.

Fatty acid turnover, substrate oxidation, and heat production in lean and obese cats during the euglycemic hyperinsulinemic clamp

Simultaneous application of the euglycemic hyperinsulinemic clamp (EHC) and indirect calorimetry was used to examine heat production, fat, and glucose metabolism in lean and obese adult neutered male and female cats. The results show that in lean insulin-sensitive cats glucose oxidation predominated during fasting, whereas lipid oxidation became more prominent in obese cats. Insulin infusion during the EHC in lean cats and obese male cats led to a large increase in glucose oxidation, glycogenesis, and lipogenesis. It also led to an increase in glucose oxidation and glycogenesis in obese female cats but it was significantly less compared to lean cats and obese males. This indicates that obese females show greater metabolic inflexibility. In obese cats of either gender, insulin caused greater suppression of non-esterified fatty acids compared to lean cats suggesting that obese cats show greater fatty acid clearance than lean cats. The heat production per metabolic size was lower in obese cats than lean cats. This would perpetuate obesity unless food intake is decreased. The higher glucose oxidation rate in obese neutered male cats suggests that they are able to replete their glycogen and lipid stores at a faster rate than females in response to insulin and it implies that they gain weight more rapidly. Further studies are needed to investigate if the different response to insulin of male cats is involved in their higher risk to develop diabetes.

Markers of mitochondrial biogenesis and metabolism are lower in overweight and obese insulin-resistant subjects

BACKGROUND

Impaired mitochondrial function in skeletal muscle is implicated in the development of insulin resistance. However, potential differences in fatness and fitness may influence previous results.

METHODS

Subjects (n=18) were divided into insulin-sensitive (IS) and insulin-resistant (IR) groups by median glucose infusion rate during a hyperinsulinemic euglycemic clamp. Weight, VO2max (maximal aerobic capacity), and percentage body fat were measured before and after 6 continuous weeks of aerobic exercise training at 55-70% VO2max (40 min/session, 4 d/wk).

RESULTS

Age, percentage fat, and VO2max were not different between IS and IR groups at baseline. Expression of the nuclear encoded PGC1alpha and mitochondrial encoded gene COX1 were significantly lower in the IR group (P<0.05). Citrate synthase activity and protein levels of subunits from complexes I and III of the respiratory chain were also lower in the IR group (P<0.05). Insulin sensitivity and aerobic fitness were increased after exercise training in both groups (P<0.001), and the expression of mitochondrial encoded genes CYTB and COX1 was also increased (P<0.01). However, there was no change in PGC1alpha expression, mitochondrial enzyme activity, or protein levels of complexes of the respiratory chain in response to exercise in either group.

CONCLUSION

This study confirms that IR men have reduced markers of mitochondrial metabolism, independent of fatness and fitness. Moderate exercise training did not alter these markers despite improving fitness and whole body insulin sensitivity. This study suggests that additional mechanisms may be involved in improving insulin resistance after exercise training in obese men.

Uncoupling protein 3 and physical activity: the role of uncoupling protein 3 in energy metabolism revisited

Physical activity influences energy metabolism in human subjects by increasing activity-induced energy expenditure and resting metabolic rate for several hours after exercise. On the other hand, physical activity increases mechanical energy efficiency, suggesting that trained subjects would need less energy for daily activities. The underlying mechanism by which physical activity influences energy metabolism is largely unknown. The skeletal muscle-specific homologue of uncoupling protein (UCP) 1, UCP3, could possibly play a major role in energy expenditure. UCP3 is, like UCP1, able to uncouple respiration from ATP production. A strong link or association between theUCP3gene and energy metabolism was found. Furthermore, UCP3 mRNA expression is related to sleeping metabolic rate, and thyroid hormone, a powerful stimulator of energy expenditure, up regulates UCP3. Finally, mice overexpressing UCP3 are hyperphagic but lean. These findings indicated that UCP3 is related to energy metabolism and that UCP3 could have a role in the effect of physical activity on energy expenditure. Thus, acute exercise up regulates UCP3, whereas endurance training results in the down-regulation of UCP3 protein content. Only a minimal amount of physical activity is needed for down-regulation of UCP3. Moreover, there is very strong evidence that UCP3 is negatively related to mechanical energy efficiency, suggesting that the down-regulation of UCP3 with training increases mechanical energy efficiency. Taken together, although the exact function of UCP3 is still unknown, exercise and training studies clearly show that under certain circumstances UCP3 is strongly related to human energy metabolism, possibly as a secondary effect of its (yet) unknown primary function.

Impaired fat-induced thermogenesis in obese subjects: the NUGENOB study

OBJECTIVES

To study energy expenditure before and 3 hours after a high-fat load in a large cohort of obese subjects (n = 701) and a lean reference group (n = 113).

RESEARCH METHODS AND PROCEDURES

Subjects from seven European countries underwent a 1-day clinical study with a liquid test meal challenge containing 95% fat (energy content was 50% of estimated resting energy expenditure). Fasting and 3-hour postprandial energy expenditures, as well as metabolites and hormones, were determined.

RESULTS

Obese subjects had a reduced postprandial energy expenditure after the high-fat load, independent of body composition, age, sex, research center, and resting energy expenditure, whereas within the obese group, thermogenesis increased again with increasing BMI category. Additionally, insulin resistance, habitual physical activity, postprandial plasma triacylglycerols, and insulin were all independently positively related to the postprandial energy expenditure. Resting energy expenditure, adjusted for fat-free mass, increased with degree of obesity, a difference that disappeared after adjustment for fat mass. Furthermore, insulin resistance, fasting plasma free fatty acids, and cortisol were positively associated, whereas fasting plasma leptin and insulin-like growth factor-1 were negatively associated, with resting energy expenditure.

DISCUSSION

The 3-hour fat-induced thermogenic response is reduced in obesity. It remains to be determined whether this blunted thermogenic response is a contributory factor or an adaptive response to the obese state.

Short-term, increasing dietary protein and fat moderately affect energy expenditure, substrate oxidation and uncoupling protein gene expression in rats

Macronutrient composition of diets can influence body-weight development and energy balance. We studied the short-term effects of high-protein (HP) and/or high-fat (HF) diets on energy expenditure (EE) and uncoupling protein (UCP1-3) gene expression. Adult male rats were fed ad libitum with diets containing different protein-fat ratios: adequate protein-normal fat (AP-NF): 20% casein, 5% fat; adequate protein-high fat (AP-HF): 20% casein, 17% fat; high protein-normal fat (HP-NF): 60% casein, 5% fat; high protein-high fat (HP-HF): 60% casein, 17% fat. Wheat starch was used for adjustment of energy content. After 4 days, overnight EE and oxygen consumption, as measured by indirect calorimetry, were higher and body-weight gain was lower in rats fed with HP diets as compared with rats fed diets with adequate protein content (P<.05). Exchanging carbohydrates by protein increased fat oxidation in HF diet fed groups. The UCP1 mRNA expression in brown adipose tissue was not significantly different in HP diet fed groups as compared with AP diet fed groups. Expression of different homologues of UCPs positively correlated with nighttime oxygen consumption and EE. Moreover, dietary protein and fat distinctly influenced liver UCP2 and skeletal muscle UCP3 mRNA expressions. These findings demonstrated that a 4-day ad libitum high dietary protein exposure influences energy balance in rats. A function of UCPs in energy balance and dissipating food energy was suggested. Future experiments are focused on the regulation of UCP gene expression by dietary protein, which could be important for body-weight management.

Electroacupuncture suppresses expression of gastric ghrelin and hypothalamic NPY in chronic food restricted rats

Electroacupuncture (EA) has been reported to reduce body weight in overweight subjects in clinical practice, as well as in rats and mice with diet-induced obesity. In the present study, this effect of EA was tested in lean rats subjected to long-term food restriction (FR, food was offered only 1 h/day). Two hertz EA administered once every other day produced a further reduction in body weight in FR rats. Exploration of the mechanism involved revealed significant downregulation of the orexigenic peptides: ghrelin in the stomach, and neuropeptide Y (NPY) but not Agouti-related peptide (AgRP) in the hypothalamus, which was in line with the reduction in food intake in rats receiving EA stimulation as compared with those receiving restraint only. Uncoupling protein 3 (UCP3), involved in accelerating energy expenditure, was not significantly altered. These results suggest that the EA-induced body weight reduction was due mainly to a decrease in food intake rather than an increase in energy expenditure. A reduction in the orexigenic peptides ghrelin and NPY may be involved in the underlying mechanism.

Liver PPARα and UCP2 are involved in the regulation of obesity and lipid metabolism by swim training in genetically obese db/db mice

Swim training for 6 weeks significantly decreased body weight gain, adipose tissue mass, and adipocyte size in both sexes of genetically obese db/db mice compared with their respective sedentary controls. Swim training also caused significant decreases in serum levels of free fatty acids, triglycerides, and total cholesterol in both sexes of obese mice. Concomitantly, hepatic mRNA levels of peroxisome proliferator-activated receptor alpha (PPARalpha) target enzymes responsible for mitochondrial and peroxisomal fatty acid beta-oxidation were significantly increased by swim training. Moreover, mRNA levels of uncoupling protein 2 (UCP2) in liver were also markedly increased by swim training. In conclusion, these results suggest that swim training-induced transcriptional activation of hepatic PPARalpha target enzymes and UCP2 may effectively prevent body weight gain, adiposity, and lipid disorders caused by leptin receptor deficiency in both sexes of mice.

Post-genomic approaches to understanding the mechanisms of environmentally induced phenotypic plasticity

Post-genomic techniques offer new and detailed insights into the mechanisms underpinning all biological processes, including phenotypic plasticity and environmentally relevant phenotypes. Although they require access to genomic resources it is now possible to create these for species of comparative or environmental interest even within a modest research project. Here we describe an open transcript screen for genes responding to environmental cold that might account for the acquired cold-specific phenotype in all its complex manifestations. Construction of a cDNA microarray led to a survey of transcript expression levels in seven tissues of carp, as a function of time,and three different extents of cooling. The resulting data delineated a common stress response found in all tissues that comprises genes involved in cellular homeostasis, including energy charge, ATP turnover, protein turnover and stress protein production. These genes respond to kinds of perturbation other than cold and probably form part of a more general stress response common to other species. We also defined tissue-specific response patterns of transcript regulation whose main characteristics were investigated by a profiling technique based on categorisation of gene function. These genes underpin the highly tissue-specific pattern of physiological adaptations observed in the cold-acclimated fish. As a result we have identified a large number of candidate gene targets with which to investigate adaptive responses to environmental challenge.

Fenofibrate activates the biochemical pathways and the de novo expression of genes related to lipid handling and uncoupling protein-3 functions in liver of normal rats

Fibrates (anti-hyperlipidemic agents) enhance the mRNA expression of uncoupling protein 2 (UCP2) in the liver and that of uncoupling protein 3 (UCP3) in skeletal muscle in standard-diet-fed rats and induce a de novo expression of UCP3 (mRNA and protein) in the liver of high-fat-fed rats. Here, we report that in the liver of normal rats, fenofibrate induces a de novo expression of UCP3 and a 6-fold increase in UCP2 mRNA, whereas UCP2 protein was not detectable. Indeed, we evidenced an ORF in UCP2 exon 2 potentially able to inhibit the expression of the protein. Fenofibrate increases the expression and activity of hepatic enzymes and cofactors involved in lipid handling and UCP3 activity and, as is the case for UCP3, induces other muscle-specific genes (e.g., Carnitine palmitoyl transferase 1b and Ubiquinone biosynthesis protein COQ7 homolog). In addition, we demonstrated that in mitochondria from fenofibrate-treated rats a palmitoyl-carnitine-induced GDP-sensitive uncoupling takes place, involving UCP3 rather than other uncouplers (i.e., UCP2 and Adenine Nucleotide Translocase). Thus, the liver of fenofibrate-treated standard-diet- fed rat is a useful model for investigations of the biochemical functions of UCP3 and allowed us to demonstrate that fenofibrate programs a gene-expression pattern able to modulate lipid handling and UCP3 activation.

Exercise training restores uncoupling protein-3 content in limb muscles of patients with chronic obstructive pulmonary disease

Oxidative capacity and uncoupling protein-3 (UCP3) content are reduced in limb muscles of patients with chronic obstructive pulmonary disease (COPD). It has been hypothesized that the physiological role of UCP3 is to protect mitochondria against lipotoxicity in cases where fatty acid influx exceeds the capacity to oxidize them. Exercise training improves oxidative capacity and reduces UCP3 protein content in healthy subjects, but the response of UCP3 to training in COPD is unknown. We studied the effect of exercise training on UCP3 content in limb muscles of COPD patients. For this, seven healthy age-matched subjects and thirteen patients with COPD were studied. All patients were admitted to an 8-wk exercise training intervention. Exercise capacity was assessed by means of an incremental cycle ergometry test. Biopsies were taken from the vastus lateralis in which UCP3 and lipid peroxidation levels were determined by Western blotting. Citrate synthase and 3-hydroxyacyl-CoA dehydrogenase (HAD; an enzyme involved in fatty acid oxidation) were measured as indexes of muscle oxidative capacity. UCP3 in COPD was approximately 50% lower compared with healthy age-matched controls. In COPD, training induced upregulation of UCP3 [from 67.7 (SD 41.8) to 113.8 (SD 104.2) arbitrary units (AU), P = 0.062], especially in the patients who showed no increase in HAD activity [from 80.9 (SD 52.6) to 167.9 (SD 109.1) AU, P = 0.028], whereas lipid peroxidation levels remained unaltered. We conclude that exercise-training can restore muscle UCP3 protein level in COPD, and the nature of this response complies with the hypothesis that UCP3 may protect against lipotoxicity.

NO-1886 (ibrolipim), a lipoprotein lipase-promoting agent, accelerates the expression of UCP3 messenger RNA and ameliorates obesity in ovariectomized rats

The synthetic compound NO-1886 (ibrolipim, [4-(4-bromo-2-cyano-phenylcarbamoyl)-benzyl]-phosphonic acid diethyl ester, CAS 133208-93-2) is a lipoprotein lipase (LPL)-promoting agent that decreases plasma triglycerides, increases high-density lipoprotein cholesterol levels, and prevents fat accumulation in high fat-fed rats. However, the effect of NO-1886 on body weight, fat accumulation, and energy expenditure in ovariectomized (OVX) rats is not clear. The primary aim of this study was to ascertain whether NO-1886 ameliorated obesity in OVX rats and to examine the effects on fatty acid oxidation-related enzymes. NO-1886 decreased accumulation of visceral fat and suppressed the increase in body weight resulting from the ovariectomy. NO-1886 decreased the respiratory quotient and increased expression of the fatty acid translocase messenger RNA (mRNA) in the liver, soleus muscle, and mesenteric fat. NO-1886 also increased the expression of fatty acid-binding protein mRNA in the liver and soleus muscle and the expression of the uncoupling protein 3 (UCP3) mRNA in the heart, soleus muscle, and mesenteric fat, but not in the brown adipose tissue. Furthermore, NO-1886 did not affect UCP1 and UCP2 in brown adipose tissue. Therefore, amelioration of obesity by NO-1886 in OVX rats is possibly because of an the increased expression of fatty acid oxidation-related enzymes and UCP3, both of which are related to fatty acid transfer and fat use. Our study indicates that the LPL-promoting agent NO-1886 may be potentially beneficial in the treatment of obesity and obesity-linked health problems in postmenopausal women.

Thyroid hormones as molecular determinants of thermogenesis

Thyroid hormones (TH) are major modulators of energy metabolism and thermogenesis. It is generally believed that 3,5,3'-triiodo-l-thyronine (T3) is the only active form of TH, and that most of its effects are mediated by nuclear T3 receptors, which chiefly affect the transcription of target genes. Some of these genes encode for the proteins involved in energy metabolism. However, a growing volume of evidence now indicates that other iodothyronines may be biologically active. Several mechanisms have been proposed to explain the calorigenic effect of TH, but none has received universal acceptance. Cold acclimation/exposure and altered nutritional status are physiological conditions in which a modulation of energy expenditure is particularly important. TH seem to be deeply involved in this modulation, and this article will review some aspects of their possible influence in these conditions.