Rita Rinnankoski-Tuikka

Effects of diet-induced obesity and voluntary wheel running on the microstructure of the murine distal femur

BackgroundObesity and osteoporosis, two possibly related conditions, are rapidly expanding health concerns in modern society. Both of them are associated with sedentary life style and nutrition. To investigate the effects of diet-induced obesity and voluntary physical activity we used high resolution micro-computed tomography (μCT) together with peripheral quantitative computed tomography (pQCT) to examine the microstructure of the distal femoral metaphysis in mice.MethodsForty 7-week-old male C57BL/6J mice were assigned to 4 groups: control (C), control + running (CR), high-fat diet (HF), and high-fat diet + running (HFR). After a 21-week intervention, all the mice were sacrificed and the left femur dissected for pQCT and μCT measurements.ResultsThe mice fed the high-fat diet showed a significant weight gain (over 70% for HF and 60% for HFR), with increased epididymal fat pad mass and impaired insulin sensitivity. These obese mice had significantly higher trabecular connectivity density, volume, number, thickness, area and mass, and smaller trabecular separation. At the whole bone level, they had larger bone circumference and cross-sectional area and higher density-weighted maximal, minimal, and polar moments of inertia. Voluntary wheel running decreased all the cortical bone parameters, but increased the trabecular mineral density, and decreased the pattern factor and structure model index towards a more plate-like structure.ConclusionsThe results suggest that in mice the femur adapts to obesity by improving bone strength both at the whole bone and micro-structural level. Adaptation to running exercise manifests itself in increased trabecular density and improved 3D structure, but in a limited overall bone growth

Gene expression centroids that link with low intrinsic aerobic exercise capacity and complex disease risk

A strong link exists between low aerobic exercise capacity and complex metabolic diseases. To probe this linkage, we utilized rat models of low and high intrinsic aerobic endurance running capacity that differ also in the risk for metabolic syndrome. We investigated in skeletal muscle gene‐phenotype relationships that connect aerobic endurance capacity with metabolic disease risk factors. The study compared 12 high capacity runners (HCRs) and 12 low capacity runners (LCRs) from generation 18 of selection that differed by 615% for maximal treadmill endurance running capacity. On average, LCRs were heavier and had increased blood glucose, insulin, and triglycerides compared with HCRs. HCRs were higher for resting metabolic rate, voluntary activity, serum high density lipoproteins, muscle capillarity, and mitochondrial area. Bioinformatic analysis of skeletal muscle gene expression data revealed that many genes up‐regulated in HCRs were related to oxidative energy metabolism. Seven mean mRNA expression centroids, including oxidative phosphorylation and fatty acid metabolism, correlated significantly with several exercise capacity and disease risk phenotypes. These expression‐phenotype correlations, together with diminished skeletal muscle capillarity and mitochondrial area in LCR rats, support the general hypothesis that an inherited intrinsic aerobic capacity can underlie disease risks.—Kivelä, R., Silvennoinen, M., Lehti, M., Rinnankoski‐Tuikka, R., Purhonen, T., Ketola, T., Pullinen, K., Vuento, M., Mutanen, N., Sartor, M. A., Reunanen, H., Koch, L. G., Britton, S. L., Kainulainen, H. Gene expression centroids that link with low intrinsic aerobic exercise capacity and complex disease risk. FASEB J. 24, 4565–4574 (2010). www.fasebj.org

Differences in Muscle and Adipose Tissue Gene Expression and Cardio-Metabolic Risk Factors in the Members of Physical Activity Discordant Twin Pairs

High physical activity/aerobic fitness predicts low morbidity and mortality. Our aim was to identify the most up-regulated gene sets related to long-term physical activity vs. inactivity in skeletal muscle and adipose tissues and to obtain further information about their link with cardio-metabolic risk factors. We studied ten same-sex twin pairs (age range 50–74 years) who had been discordant for leisure-time physical activity for 30 years. The examinations included biopsies from m. vastus lateralis and abdominal subcutaneous adipose tissue. RNA was analyzed with the genome-wide Illumina Human WG-6 v3.0 Expression BeadChip. For pathway analysis we used Gene Set Enrichment Analysis utilizing active vs. inactive co-twin gene expression ratios. Our findings showed that among the physically active members of twin pairs, as compared to their inactive co-twins, gene expression in the muscle tissue samples was chronically up-regulated for the central pathways related to energy metabolism, including oxidative phosphorylation, lipid metabolism and supportive metabolic pathways. Up-regulation of these pathways was associated in particular with aerobic fitness and high HDL cholesterol levels. In fat tissue we found physical activity-associated increases in the expression of polyunsaturated fatty acid metabolism and branched-chain amino acid degradation gene sets both of which associated with decreased ‘high-risk’ ectopic body fat and plasma glucose levels. Consistent with other findings, plasma lipidomics analysis showed up-regulation of the triacylglycerols containing the polyunsaturated fatty acids. Our findings identified skeletal muscle and fat tissue pathways which are associated with the long-term physical activity and reduced cardio-metabolic disease risk, including increased aerobic fitness. In particular, improved skeletal muscle oxidative energy and lipid metabolism as well as changes in adipocyte function and redistribution of body fat are associated with reduced cardio-metabolic risk.

Obesity Is Associated With Low NAD+/SIRT Pathway Expression in Adipose Tissue of BMI-Discordant Monozygotic Twins

CONTEXT Sirtuins (SIRTs) regulate cellular metabolism and mitochondrial function according to the energy state of the cell reflected by NAD(+) levels. OBJECTIVE Our aim was to determine whether expressions of SIRTs and NAD(+) biosynthesis genes are affected by acquired obesity and how possible alterations are connected with metabolic dysfunction while controlling for genetic and familial factors. DESIGN AND PARTICIPANTS We studied a cross-sectional sample of 40 healthy pairs of monozygotic twins, including 26 pairs who were discordant for body mass index (within-pair difference > 3 kg/m(2)), from the FinnTwin12 and FinnTwin16 cohorts. MAIN OUTCOME MEASURES Subcutaneous adipose tissue (SAT) transcriptomics was analyzed by using Affymetrix U133 Plus 2.0 chips, total SAT (poly-ADP) ribose polymerase (PARP) activity by an ELISA kit, body composition by dual-energy x-ray absorptiometry and magnetic resonance imaging/spectroscopy, and insulin sensitivity by an oral glucose tolerance test. RESULTS SIRT1, SIRT3, SIRT5, NAMPT, NMNAT2, NMNAT3, and NRK1 expressions were significantly down-regulated and the activity of main cellular NAD(+) consumers, PARPs, trended to be higher in the SAT of heavier co-twins of body mass index-discordant pairs. Controlling for twin-shared factors, SIRT1, SIRT3, NAMPT, NMNAT3, and NRK1 were significantly negatively correlated with adiposity, SIRT1, SIRT5, NMNAT2, NMNAT3, and NRK1 were negatively correlated with inflammation, and SIRT1 and SIRT5 were positively correlated with insulin sensitivity. Expressions of genes involved in mitochondrial unfolded protein response were also significantly down-regulated in the heavier co-twins. CONCLUSIONS Our data highlight a strong relationship of reduced NAD(+)/SIRT pathway expression with acquired obesity, inflammation, insulin resistance, and impaired mitochondrial protein homeostasis in SAT.

Effects of high-fat diet and physical activity on pyruvate dehydrogenase kinase-4 in mouse skeletal muscle

BackgroundThe expression of PDK4 is elevated by diabetes, fasting and other conditions associated with the switch from the utilization of glucose to fatty acids as an energy source. It is previously shown that peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), a master regulator of energy metabolism, coactivates in cell lines pyruvate dehydrogenase kinase-4 (PDK4) gene expression via the estrogen-related receptor α (ERRα). We investigated the effects of long-term high-fat diet and physical activity on the expression of PDK4, PGC-1α and ERRα and the amount and function of mitochondria in skeletal muscle.MethodsInsulin resistance was induced by a high-fat (HF) diet for 19 weeks in C57BL/6 J mice, which were either sedentary or with access to running wheels. The skeletal muscle expression levels of PDK4, PGC-1α and ERRα were measured and the quality and quantity of mitochondrial function was assessed.ResultsThe HF mice were more insulin-resistant than the low-fat (LF) -fed mice. Upregulation of PDK4 and ERRα mRNA and protein levels were seen after the HF diet, and when combined with running even more profound effects on the mRNA expression levels were observed. Chronic HF feeding and voluntary running did not have significant effects on PGC-1α mRNA or protein levels. No remarkable difference was found in the amount or function of mitochondria.ConclusionsOur results support the view that insulin resistance is not mediated by the decreased qualitative or quantitative properties of mitochondria. Instead, the role of PDK4 should be contemplated as a possible contributor to high-fat diet-induced insulin resistance.

Weight Loss Is Associated With Increased NAD+/SIRT1 Expression But Reduced PARP Activity in White Adipose Tissue

CONTEXT Sirtuins (SIRTs) and poly(ADP-ribose) polymerases (PARPs) are 2 important nicotinamide adenine dinucleotide (NAD)(+)-dependent enzyme families with opposing metabolic effects. Energy shortage increases NAD(+) biosynthesis and SIRT activity but reduces PARP activity in animals. Effects of energy balance on these pathways in humans are unknown. OBJECTIVE We compared NAD(+)/SIRT pathway expressions and PARP activities in sc adipose tissue (SAT) between lean and obese subjects and investigated their change in the obese subjects during a 12-month weight loss. DESIGN, SETTING AND PARTICIPANTS SAT biopsies were obtained from 19 clinically healthy obese subjects (mean ± SE body mass index, 34.6 ± 2.7 kg/m(2)) during a weight-loss intervention (0, 5, and 12 mo) and from 19 lean reference subjects (body mass index, 22.7 ± 1.1 kg/m(2)) at baseline. MAIN OUTCOME MEASURES SAT mRNA expressions of SIRTs 1-7 and the rate-limiting gene in NAD(+) biosynthesis, nicotinamide phosphoribosyltransferase (NAMPT) were measured by Affymetrix, and total PARP activity by ELISA kit. RESULTS SIRT1, SIRT3, SIRT7, and NAMPT expressions were significantly lower, whereas total PARP activity was increased in obese compared with lean subjects. SIRT1 and NAMPT expressions increased in obese subjects between 0 and 5 months, after a mean weight loss of 11.7%. In subjects who continued to lose weight between 5 and 12 months, SIRT1 expression increased progressively, whereas in subjects with weight regain, SIRT1 reverted to baseline levels. PARP activity significantly decreased in all subjects upon weight loss. CONCLUSIONS Calorie restriction is an attractive strategy to improve the NAD(+)/SIRT pathway and decrease PARPs in SAT in human obesity.

Lipid droplet-associated proteins in high-fat fed mice with the effects of voluntary running and diet change

OBJECTIVE The relation between lipid accumulation and influence of exercise on insulin sensitivity is not straightforward. A proper balance between lipid droplet synthesis, lipolysis, and oxidative metabolism would ensure low local intramyocellular fatty acid levels, thereby possibly protecting against lipotoxicity-associated insulin resistance. This study investigated whether the accumulation of triglycerides and lipid droplets in response to high availability of fatty acids after high-fat feeding would parallel the abundance of intramyocellular perilipin proteins, especially PLIN5. The effects on these variables after diet change or voluntary running exercise intervention in skeletal muscle were also investigated. METHODS During a 19-week experiment, C57BL/6J mice were studied in six different groups: low-fat diet sedentary, low-fat diet active, high-fat diet sedentary, high-fat diet active and two groups which were high-fat sedentary for nine weeks, after which divided into low-fat sedentary or low-fat active groups. Myocellular triglyceride concentration and perilipin protein expression levels were assessed. RESULTS We show that, concurrently with impaired insulin sensitivity, the expression level of PLIN5 and muscular triglyceride concentration increased dramatically after high-fat diet. These adaptations were reversible after the diet change intervention with no additional effect of exercise. CONCLUSIONS After high-fat diet, lipid droplets become larger providing more surface area for PLIN5. We suggest that PLIN5 is an important regulator of lipid droplet turnover in altered conditions of fatty acid supply and consumption. Imbalances in lipid droplet metabolism and turnover might lead to lipotoxicity-related insulin resistance.

Voluntary Running Aids to Maintain High Body Temperature in Rats Bred for High Aerobic Capacity.

The production of heat, i.e., thermogenesis, is a significant component of the metabolic rate, which in turn affects weight gain and health. Thermogenesis is linked to physical activity (PA) level. However, it is not known whether intrinsic exercise capacity, aging, and long-term voluntary running affect core body temperature. Here we use rat models selectively bred to differ in maximal treadmill endurance running capacity (Low capacity runners, LCR and High capacity Runners, HCR), that as adults are divergent for aerobic exercise capacity, aging, and metabolic disease risk to study the connection between PA and body temperature. Ten high capacity runner (HCR) and ten low capacity runner (LCR) female rats were studied between 9 and 21 months of age. Rectal body temperature of HCR and LCR rats was measured before and after 1-year voluntary running/control intervention to explore the effects of aging and PA. Also, we determined whether injected glucose and spontaneous activity affect the body temperature differently between LCR and HCR rats at 9 vs. 21 months of age. HCRs had on average 1.3°C higher body temperature than LCRs (p < 0.001). Aging decreased the body temperature level of HCRs to similar levels with LCRs. The opportunity to run voluntarily had a significant impact on the body temperature of HCRs (p < 0.001) allowing them to maintain body temperature at a similar level as when at younger age. Compared to LCRs, HCRs were spontaneously more active, had higher relative gastrocnemius muscle mass and higher UCP2, PGC-1α, cyt c, and OXPHOS levels in the skeletal muscle (p < 0.050). These results suggest that higher PA level together with greater relative muscle mass and higher mitochondrial content/function contribute to the accumulation of heat in the HCRs. Interestingly, neither aging nor voluntary training had a significant impact on core body temperature of LCRs. However, glucose injection resulted in a lowering of the body temperature of LCRs (p < 0.050), but not that of HCRs. In conclusion, rats born with high intrinsic capacity for aerobic exercise and better health have higher body temperature compared to rats born with low exercise capacity and disease risk. Voluntary running allowed HCRs to maintain high body temperature during aging, which suggests that high PA level was crucial in maintaining the high body temperature of HCRs.