Thiazolidinediones (TZDs) are insulin-sensitizing drugs currently used to treat type 2 diabetes. They are activators of peroxisome proliferator-activated receptor (PPAR)-gamma, and adipose tissue constitutes a major site for their biological effects. PPAR coactivator (PGC)-1alpha is a transcriptional coactivator of PPARgamma and other transcription factors. It is involved in the control of mitochondrial biogenesis, and its activity has been linked to insulin sensitization. Here we report that PGC-1alpha gene expression in brown and white adipocytes is a direct target of TZDs via PPARgamma activation. Activators of the retinoid X receptor also induce PGC-1alpha gene expression. This is due to the presence of a PPARgamma-responsive element in the distal region of the PGC-1alpha gene promoter that binds PPARgamma/retinoid X receptor heterodimers. Moreover, there is a positive autoregulatory loop of control of the PGC-1alpha gene through coactivation of PPARgamma responsiveness to TZDs by PGC-1alpha itself. These data indicate that some of the effects of TZDs, especially promotion of mitochondrial biogenesis and oxidative pathways in adipose depots, entail PGC-1alpha up-regulation via enhanced transcription of the PGC-1alpha gene.

The importance of dietary fat components, such as fatty acids, in the expression of multiple genes is clear. In the case of beef cattle, fat in the form of fatty acids (saturated or unsaturated), vitamin A (mainly retinoic acid), or carotenoids (β-carotene and lutein) is obtained from dietary feed or pasture. The aim of this work was to study the effect of fatty acids (phytanic and pristanic acids), vitamin A (all-trans and 9-cis retinoic acid), and carotenoids (β-carotene and lutein) on the expression of PPARγ and its coactivator PGC-1α during differentiation of bovine white adipose tissue. Samples were collected at slaughter from subcutaneous adipose tissue and processed in a solution containing type II collagenase for 2 h at 37°C. Cells were resuspended in basal medium, Dulbecco’s modified Eagle’s medium containing 5% fetal bovine serum, plated on 24-well culture plates at a density of 1 × 10⁴ cells/cm², and incubated at 37°C in a 5% CO₂ atmosphere. Preadipocyte differentiation after reaching confluence was induced by various treatments: rosiglitazone (20 μM); unsaturated fatty acids: phytanic acid (25, 50, 100 μM) and pristanic acid (25, 50, 100 μM); retinoids: 9-cis retinoic acid (0.5, 0.75, 1 μM) and all-trans retinoic acid (0.5, 0.75, 1 μM); and carotenoids: β-carotene (10, 20, 30 μM) and lutein (10, 20, 30 μM). Expression of PPARγ and PGC-1α was measured in differentiated cells. Phytanic acid, all-trans retinoic acid, and 9-cis retinoic acid were the best activators of PPARγ expression, and the combination of 9-cis and all-trans retinoic acid was the best activator of PGC-1α expression (P < 0.05). Therefore, these are powerful agents for the promotion of bovine adipogenesis and constitute promising compounds to be used in bovine fattening. Copyright © 2010. American Society of Animal Science .

Sirtuins, the mammalian homologs of the silent information regulator 2 gene of Saccharomyces cerevisiae, are members of the NAD⁺-dependent family of histone deacetylases. In vertebrates, 7 sirtuins have been described, with different cellular localizations and target proteins. Glucose and lipid metabolism are among the processes regulated by these enzymes. In ruminants, gluconeogenesis is the main biochemical pathway by which glucose is obtained. Because sirtuins in bovines have not been studied, the aim of this work was to obtain sequences coding for the 7 sirtuins and determine the expression patterns of sirtuin1 (Sirt1) and sirtuin3 (Sirt3) in the liver, muscle, and adipose tissue of calves and bulls. Using PCR amplification, we obtained sirtuin gene sequences and reported them to the National Center for Biotechnology Information GenBank. Characteristic sequence motifs corresponding to the sirtuin catalytic core domain were found, including the active and zinc-binding sites. Relative expression patterns of Sirt1 and Sirt3 in liver, muscle, and adipose tissue were quantified by real-time PCR, normalizing to the geometric mean of the housekeeping genes cyclophilin A and β-actin. Expression of Sirt1 was less in liver and muscle, whereas it was greater in adipose tissue of adult animals, with statistical differences (P = 0.0071) only in the latter. In the case of Sirt3, expression was greater in all 3 adult tissues, but statistical differences were found only in liver (P = 0.0141) and muscle (P = 0.0017). The greatest expression was observed in liver for Sirt1 and in muscle for Sirt3, whereas the least expression was in muscle for Sirt1 and in adipose tissue for Sirt3. In other species, sirtuin expression (both Sirt1 and Sirt3) in liver is reported to be the greatest among these 3 tissues, a pattern different from what we measured. These differences in expression can be associated with metabolic differences between nonruminant and ruminant species. However, further research on the relationship between bovine sirtuins and ruminant metabolism is required for a better understanding of these fields. Copyright © 2011. American Society of Animal Science .

The main adipogenic transcription factor PPARγpossesses high affinity to 2,4-TZD, a member of the Thiazolidinedione family of insulin-sensitizing compounds used as adipogenic agents. We evaluated 2,4-TZD’s effect on bovine growth and PPAR tissue expression. Seventeen Limousin bulls (18 month-old; 350 kg body weight (BW)) were assigned into 2 treatments: control and 2,4-TZD (8 mg/70 kg BW) and were fed until bulls reached 500 kg BW. They were weighed and their blood was sampled. DNA, RNA, and protein were determined in liver; skeletal muscle; subcutaneous (SC), omental, perirenal adipose tissues (AT) to determine protein synthesis rate and cellular size. Expression of PPAR mRNA was measured in liver and muscle (PPARα, -δ, and -γ) and SC adipose tissue (γ) by real-time PCR. No significant differences were found (P>0.1) in weight gain, days on feed, and carcass quality. Muscle synthesis was greater in controls (P<0.05); cell size was larger with 2,4-TZD (P<0.05). PPARα, -δ, and -γexpressions with 2,4-TZD in liver were lower (P<0.01) than in muscle. No differences were found for PPARγmRNA expression in SCAT. The results suggest the potential use of 2,4-TZD in beef cattle diets, because it improves AT differentiation, liver, and muscle fatty acid oxidation that, therefore, might improve energy efficiency.

The consumption of cricket (Acheta domesticus, AD) has recently increased due to its high nutritional and bioactive compound contents. However, limited studies have explored the beneficial effects of AD consumption. Therefore, we aimed to evaluate the protective effect of a diet supplemented with AD flour on obesity control and its complications in an in vivo model. The chemical profiling of the AD showed an important protein content, chitin, and polyunsaturated fatty acids contents. For the in vivo study, a high-fructose and saturated fat diet (HFFD) was supplemented with AD (4% and 8%). The 8% AD supplementation reduced body weight gain (19%) and serum triglycerides (37%) in HFFD-fed rats. These benefits were related to a greater lipid excretion in feces (97%) and the partial inhibition of pancreatic lipase in vitro by the aqueous extract and the hydrolyzed proteins obtained from AD. Additionally, the 8% AD supplementation improved insulin resistance measured by the HOMA index (61%). Thus, 8% AD supplementation to HFFD-fed rats was effective in preventing obesity, dyslipidemia, and insulin resistance. PRACTICAL APPLICATIONS: Obesity is a risk factor for developing insulin resistance and dyslipidemia. Therefore, there is an increasing interest in consuming foods rich in bioactive compounds as therapeutic alternatives for managing the development of obesity and its complications. Edible insects, such as crickets, are attractive for treating obesity due to their content of protein, fiber, and polyunsaturated fatty acids. Studies have explored the effect of glycosaminoglycan (GAG)-enriched extracts from the cricket Gryllus bimaculatus against obesity. However, GAG content in crickets is low, and crickets are commonly consumed whole instead of extracts. The cricket Acheta domesticus (AD) is among the most rearing cricket species as it is easy to farm and has a better flavor. However, limited studies have explored the beneficial effects of AD consumption. This study demonstrates that AD prevents obesity and ameliorates dyslipidemia and insulin resistance. Therefore, AD is a valuable entomotherapeutic strategy to reduce the comorbidities associated with diet-induced obesity.