Childhood obesity and insulin resistance in a Yucatan mini-piglet model: putative roles of IGF-1 and muscle PPARs in adipose tissue activity and development

Transcriptomics and Selection Pressure Analysis Reveals the Influence Mechanism of PLIN1 Protein on the Development of Small Size in Min Pigs

Body size is an important biological phenotypic trait that has attracted substantial attention. Small domestic pigs can serve as excellent animal models for biomedicine and also help meet sacrificial culture needs in human societies. Although the mechanisms underlying vertebral development regulating body size variation in domestic pigs during the embryonic period have been well described, few studies have examined the genetic basis of body size variation in post embryonic developmental stages. In this study, seven candidate genes-PLIN1, LIPE, PNPLA1, SCD, FABP5, KRT10 and IVL-significantly associated with body size were identified in Min pigs, on the basis of weighted gene co-expression network analysis (WGCNA), and most of their functions were found to be associated with lipid deposition. Six candidate genes except for IVL were found to have been subjected to purifying selection. PLIN1 had the lowest ω value (0.139) and showed heterogeneous selective pressure among domestic pig lineages with different body sizes (p < 0.05). These results suggested that PLIN1 is an important genetic factor regulating lipid deposition and consequently affecting body size variation in pigs. The culture of whole pig sacrifice in Manchu during the Qing Dynasty in China might have contributed to the strong artificial domestication and selection of Hebao pigs.

Peripheral Gonadotropin-Inhibitory Hormone (GnIH) Acting as a Novel Modulator Involved in Hyperphagia-Induced Obesity and Associated Disorders of Metabolism in an In Vivo Female Piglet Model

Apart from the well-established role of the gonadotropin-inhibitory hormone (GnIH) in the regulation of the reproductive functions, much less is known about the peripheral role of the GnIH and its receptor in the metabolic processes. On account of pig being an excellent model for studies of food intake and obesity in humans, we investigated the peripheral effects of the GnIH on food intake and energy homeostasis and revealed the underlying mechanism(s) in female piglets in vivo. Compared to the vehicle-treated group, intraperitoneally injected GnIH significantly increased the food intake and altered the meal microstructure both in the fasting and ad libitum female piglet. GnIH-triggered hyperphagia induced female piglet obesity and altered islet hormone secretion in the pancreas, accompanied with dyslipidemia and hyperglycemia. Interestingly, GnIH decreased the glucose transport capacity and glycogen synthesis, whereas it increased the gluconeogenesis in the liver, while it also induced an insulin resistance in white adipose tissue (WAT) via inhibiting the activity of AKT-GSK3-β signaling. In terms of the lipid metabolism, GnIH reduced the oxidation of fatty acids, whereas the elevated fat synthesis ability in the liver and WAT was developed though the inhibited AMPK phosphorylation. Our findings demonstrate that peripheral GnIH could trigger hyperphagia-induced obesity and an associated glycolipid metabolism disorder in female piglets, suggesting that GnIH may act as a potential therapeutic agent for metabolic syndrome, obesity and diabetes.

Obesity Development and Signs of Metabolic Abnormalities in Young Göttingen Minipigs Consuming Energy Dense Diets Varying in Carbohydrate Quality

Consumption of fructose has been associated with a higher risk of developing obesity and metabolic syndrome (MetS). The aim of this study was to examine the long-term effects of fructose compared to starch from high-amylose maize starch (HiMaize) at ad libitum feeding in a juvenile Göttingen Minipig model with 20% of the diet provided as fructose as a high-risk diet (HR, n = 15) and 20% as HiMaize as a lower-risk control diet (LR, n = 15). The intake of metabolizable energy was on average similar (p = 0.11) among diets despite increased levels of the satiety hormone PYY measured in plasma (p = 0.0005) of the LR pigs. However, after over 20 weeks of ad libitum feeding, no difference between diets was observed in daily weight gain (p = 0.103), and a difference in BW was observed only at the end of the experiment. The ad libitum feeding promoted an obese phenotype over time in both groups with increased plasma levels of glucose (p = 0.005), fructosamine (p < 0.001), insulin (p = 0.03), and HOMA-IR (p = 0.02), whereas the clinical markers of dyslipidemia were unaffected. When compared to the LR diet, fructose did not accelerate the progression of MetS associated parameters and largely failed to change markers that indicate a stimulated de novo lipogenesis.

Adiposity, reproductive and metabolic health, and activity levels in zoo Asian elephant (Elephas maximus)

Many captive Asian elephant populations are not self-sustaining, possibly due in part to obesity-related health and reproductive issues. This study investigated relationships between estimated body composition and metabolic function, inflammatory markers, ovarian activity (females only) and physical activity levels in 44 Asian elephants (n=35 females, n=9 males). Deuterium dilution was used to measure total body water from which fat mass (FM) and fat-free mass (FFM) could be derived to estimate body composition. Serum was analyzed for progestagens and estradiol (females only), deuterium, glucose, insulin and amyloid A. Physical activity was assessed by an accelerometer placed on the elephant's front leg for at least 2 days. Relative fat mass (RFM) - the amount of fat relative to body mass - was calculated to take differences in body size between elephants into consideration. Body fat percentage ranged from 2.01% to 24.59%. Male elephants were heavier (P=0.043), with more FFM (P=0.049), but not FM (P>0.999), than females. For all elephants, estimated RFM (r=0.45, P=0.004) was positively correlated with insulin. Distance walked was negatively correlated with age (r=-0.46, P=0.007). When adjusted for FFM and age (P<0.001), non-cycling females had less fat compared with cycling females, such that for every 100 kg increase in FM, the odds of cycling were 3 times higher (P<0.001). More work is needed to determine what an unhealthy amount of fat is for elephants; however, our results suggest higher adiposity may contribute to metabolic perturbations.

Dietary fibre and protein do not synergistically influence insulin, metabolic or inflammatory biomarkers in young obese Göttingen minipigs

The effects of dietary fibre (DF) and protein on insulin response, lipidaemia and inflammatory biomarkers were studied in a model experiment with juvenile obese Göttingen minipigs. After 20 weeks feeding on a high-fat fructose-rich low-DF diet, forty-three 30-week-old minipigs (31·3 (sem 4·0) kg body weight) were allocated to low- or high-DF and -protein diets for 8 weeks in a 2 × 2 factorial design. High DF contents decreased (P = 0·006) while high protein increased (P < 0·001) the daily gain. High protein contents increased fasting plasma concentrations of glucose (P = 0·008), NEFA (P = 0·015), ghrelin (P = 0·008) and non-fasting LDL:HDL ratios (P = 0·015). High DF increased ghrelin (P = 0·036) and C-peptide levels (P = 0·011) in the non-fasting state. High protein increased the gene expression of fructose-bisphosphatase 1 in liver tissue (P = 0·043), whereas DF decreased fatty acid synthase expression in adipose tissue (P = 0·035). Interactions between DF and protein level were observed in the expression of leptin receptor in adipose tissue (P = 0·031) and of PPARγ in muscle (P = 0·018) and adipose tissue (P = 0·004). In conclusion, high DF intake reduced weight gain and had potential benefit on β-cell secretory function, but without effect on the lipid profile in this young obese model. High dietary protein by supplementing with whey protein did not improve insulin sensitivity or lipidaemia, and combining high DF with high protein did not alleviate the risk of metabolic abnormalities.

Fat and carbohydrate content in the diet induces drastic changes in gene expression in young Göttingen minipigs

In human health, there is interest in developing specific diets to reduce body weight. These studies are mainly focused on phenotypic changes induced in blood measurements, i.e., triglycerides, HDL, LDL, and insulin, and on physical changes, i.e., body weight and BMI. To evaluate the biological impact of diet interventions, it is very important to investigate the molecular mechanisms driving the diet-induced phenotypic changes in relevant tissues. However, studying these effects in humans is difficult due to ethical concerns in doing interventions and obtaining tissue samples and good animal models are therefore needed. Göttingen minipigs, a small size obesity prone pig breed, have previously been shown to be a useful translational animal model for metabolic studies. In this study, 16 Göttingen minipig males (2-month old) were submitted to 13 weeks of differential diets to investigate the initial stages of diet-induced metabolic changes. Half of them were fed a high-fat/cholesterol, low-carbohydrate (HFLC) diet, and the other half were fed a low- fat/cholesterol, high-carbohydrate (LFHC) diet. After 13 weeks, the HFLC group weighted less and had dyslipidemia compared to the LFHC group. Liver, pancreas, and adipose tissues were collected at slaughter. Gene expression profiling of 83 metabolism-relevant genes was performed using high-throughput qPCR. In total, 41 genes were deregulated in at least one of the five tissues analyzed, with liver being the most drastically affected tissue. The new knowledge gained in this study could potentially be of value for considering direct modulation of gene expression by nutrient content in the diet.

DNA methylation landscape of fat deposits and fatty acid composition in obese and lean pigs

Obese and lean type pig breeds exhibit differences in their fat deposits and fatty acid composition. Here, we compared the effect of genome-wide DNA methylation on fatty acid metabolism between Landrace pigs (LP, leaner) and Rongchang pigs (RP, fatty). We found that LP backfat (LBF) had a higher polyunsaturated fatty acid content but a lower adipocyte volume than RP backfat (RBF). LBF exhibited higher global DNA methylation levels at the genome level than RBF. A total of 483 differentially methylated regions (DMRs) were located in promoter regions, mainly affecting olfactory and sensory activity and lipid metabolism. In LBF, the promoters of genes related to ATPase activity had significantly stronger methylation. This fact may suggest lower energy metabolism levels, which may result in less efficient lipid synthesis in LBF. Furthermore, we identified a DMR in the miR-4335 and miR-378 promoters and validated their methylation status by bisulfite sequencing PCR. The hypermethylation of the promoters of miR-4335 and miR-378 in LBF and the resulting silencing of the target genes may result in LBF's low content in saturated fatty acids and fat deposition capacity. This study provides a solid basis for exploring the epigenetic mechanisms affecting fat deposition and fatty acid composition.

Effects of Chronic Consumption of Sugar-Enriched Diets on Brain Metabolism and Insulin Sensitivity in Adult Yucatan Minipigs

Excessive sugar intake might increase the risk to develop eating disorders via an altered reward circuitry, but it remains unknown whether different sugar sources induce different neural effects and whether these effects are dependent from body weight. Therefore, we compared the effects of three high-fat and isocaloric diets varying only in their carbohydrate sources on brain activity of reward-related regions, and assessed whether brain activity is dependent on insulin sensitivity. Twenty-four minipigs underwent ¹⁸FDG PET brain imaging following 7-month intake of high-fat diets of which 20% in dry matter weight (36.3% of metabolisable energy) was provided by starch, glucose or fructose (n = 8 per diet). Animals were then subjected to a euglycemic hyperinsulinemic clamp to determine peripheral insulin sensitivity. After a 7-month diet treatment, all groups had substantial increases in body weight (from 36.02±0.85 to 63.33±0.81 kg; P<0.0001), regardless of the diet. All groups presented similar insulin sensitivity index (ISI = 1.39±0.10 mL·min^-1·μUI·kg). Compared to starch, chronic exposure to fructose and glucose induced bilateral brain activations, i.e. increased basal cerebral glucose metabolism, in several reward-related brain regions including the anterior and dorsolateral prefrontal cortex, the orbitofrontal cortex, the anterior cingulate cortex, the caudate and putamen. The lack of differences in insulin sensitivity index and body weight suggests that the observed differences in basal brain glucose metabolism are not related to differences in peripheral insulin sensitivity and weight gain. The differences in basal brain metabolism in reward-related brain areas suggest the onset of cerebral functional alterations induced by chronic consumption of dietary sugars. Further studies should explore the underlying mechanisms, such as the availability of intestinal and brain sugar transporter, or the appearance of addictive-like behavioral correlates of these brain functional characteristics.

Metabolic adaptations to HFHS overfeeding: how whole body and tissues postprandial metabolic flexibility adapt in Yucatan mini-pigs

PURPOSE

In the present study, we aimed to metabolically characterize the postprandial adaptations of the major tissues involved in energy, lipids and amino acids metabolisms in mini-pigs.

METHOD

Mini-pigs were fed on high-fat-high-sucrose (HFHS) diet for 2 months and several tissues explored for metabolic analyses. Further, the urine metabolome was followed over the time to picture the metabolic adaptations occurring at the whole body level following overfeeding.

RESULTS

After 2 months of HFHS consumption, mini-pigs displayed an obese phenotype characterized by high circulating insulin, triglycerides and cholesterol levels. At the tissue level, a general (muscle, adipose tissue, intestine) reduction in the capacity to phosphorylate glucose was observed. This was also supported by the enhanced hepatic gluconeogenesis potential, despite the concomitant normoglycaemia, suggesting that the high circulating insulin levels would be enough to maintain glucose homoeostasis. The HFHS feeding also resulted in a reduced capacity of two other pathways: the de novo lipogenesis, and the branched-chain amino acids transamination. Finally, the follow-up of the urine metabolome over the time allowed determining breaking points in the metabolic trajectory of the animals.

CONCLUSIONS

Several features confirmed the pertinence of the animal model, including increased body weight, adiposity and porcine obesity index. At the metabolic level, we observed a perturbed glucose and amino acid metabolism, known to be related to the onset of the obesity. The urine metabolome analyses revealed several metabolic pathways potentially involved in the obesity onset, including TCA (citrate, pantothenic acid), amino acids catabolism (cysteine, threonine, leucine).

Transmembrane protein 64 reciprocally regulates osteoblast and adipocyte differentiation by modulating Wnt/β-catenin signaling

Age-related osteoporosis is associated with a reciprocal decrease in bone formation and an increase in adiposity in the bone marrow niche. We previously reported Transmembrane protein 64 (Tmem64) to be an important regulator of osteoclast function; however, its precise role in osteoblasts has not yet been established. Here, we showed that ablation of the Tmem64 gene in mice resulted in markedly increased osteoblast and reduced adipocyte differentiation from bone marrow-derived stromal cells (BMSCs). Conversely, Tmem64 overexpression inhibited osteogenesis and accelerated adipogenesis. Furthermore, BMSCs isolated from Tmem64 knockout mice formed a greater number of colony-forming unit-osteoblasts and a lower number of colony-forming unit-adipocytes than the wild type controls. Mechanistically, the expression level of β-catenin, the key Wnt signaling molecule, increased significantly, and its nuclear translocation was enhanced in Tmem64-deficient cells. Introduction of Tmem64 significantly suppressed β-catenin-mediated transcriptional activity in an in vitro co-transfection experiment as well as during an in vivo experiment involving BAT-Gal reporter mice. These results demonstrate that Tmem64 plays an important role in the regulation of mesenchymal lineage allocation by modulating Wnt/β-catenin signaling.

Integrative neurobiology of metabolic diseases, neuroinflammation, and neurodegeneration

Alzheimer's disease (AD) is a complex, multifactorial disease with a number of leading mechanisms, including neuroinflammation, processing of amyloid precursor protein (APP) to amyloid β peptide, tau protein hyperphosphorylation, relocalization, and deposition. These mechanisms are propagated by obesity, the metabolic syndrome and type-2 diabetes mellitus. Stress, sedentariness, dietary overconsumption of saturated fat and refined sugars, and circadian derangements/disturbed sleep contribute to obesity and related metabolic diseases, but also accelerate age-related damage and senescence that all feed the risk of developing AD too. The complex and interacting mechanisms are not yet completely understood and will require further analysis. Instead of investigating AD as a mono- or oligocausal disease we should address the disease by understanding the multiple underlying mechanisms and how these interact. Future research therefore might concentrate on integrating these by “systems biology” approaches, but also to regard them from an evolutionary medicine point of view. The current review addresses several of these interacting mechanisms in animal models and compares them with clinical data giving an overview about our current knowledge and puts them into an integrated framework.

Validation of porcine knee as a sex-specific model to study human anterior cruciate ligament disorders

BACKGROUND

Animal models have long been considered an important modality for studying ACL injuries. However, to our knowledge, the value of these preclinical models to study sex-related phenomena associated with ACL injury and recovery has not been evaluated.

QUESTIONS/PURPOSES

We asked whether (1) prominent anatomic and (2) biomechanical factors differ between female and male porcine knees, particularly those known to increase the risk of ACL injury.

METHODS

Eighteen intact minipig knees (nine males, nine females) underwent MRI to determine the femoral bicondylar width, intercondylar notch size (width, area and index), medial and lateral tibial slope, ACL size (length, cross-sectional area, and volume), and medial compartment tibiofemoral cartilage thickness. AP knee laxity at 30°, 60°, and 90° flexion and ACL tensile structural properties were measured using custom-designed loading fixtures in a universal tensile testing apparatus. Comparisons between males and females were performed for all anatomic and biomechanical measures. The findings then were compared with published data from human knees.

RESULTS

Female pigs had smaller bicondylar widths (2.9 mm, ratio=0.93, effect size=-1.5) and intercondylar notches (width: 2.0 mm, ratio=0.79, effect size=-2.8; area: 30.8 mm2, ratio=0.76, effect size=-2.1; index: 0.4, ratio=0.84, effect size=-2.0), steeper lateral tibial slope (4.3°, ratio=1.13, effect size=1.1), smaller ACL (length: 2.7 mm, ratio=0.91, effect size=-1.1; area: 6.8 mm2, ratio=0.74, effect size=-1.5; volume: 266.2 mm3, ratio=0.68, effect size=-1.5), thinner medial femoral cartilage (0.4 mm, ratio=0.8, effect size=-1.1), lower ACL yield load (275 N, ratio=0.81, effect size=-1.1), and greater AP knee laxity at 30° (0.7 mm, ratio=1.32, effect size=1.1) and 90° (0.5 mm, ratio=1.24, effect size=1.1) flexion compared with their male counterparts. These differences were significant for all parameters (p≤0.04). Observed sex-related differences were similar to those reported for the human knee.

CONCLUSIONS

Significant differences exist between knees of male and female pigs with respect to prominent anatomic and biomechanical factors. Our findings strongly agreed with published data regarding human knees.

CLINICAL RELEVANCE

The findings highlight the use of the porcine large animal model to study the role of sex on ACL injuries and surgical outcome. This validated preclinical model may facilitate the development of novel, sex-specific interventions to prevent and treat ACL injuries for male and female patients.

Energy dense, protein restricted diet increases adiposity and perturbs metabolism in young, genetically lean pigs

Animal models of obesity and metabolic dysregulation during growth (or childhood) are lacking. Our objective was to increase adiposity and induce metabolic syndrome in young, genetically lean pigs. Pre-pubertal female pigs, age 35 d, were fed a high-energy diet (HED; n = 12), containing 15% tallow, 35% refined sugars and 9.1–12.9% crude protein, or a control corn-based diet (n = 11) with 12.2–19.2% crude protein for 16 wk. Initially, HED pigs self-regulated energy intake similar to controls, but by wk 5, consumed more (P<0.001) energy per kg body weight. At wk 15, pigs were subjected to an oral glucose tolerance test (OGTT); blood glucose increased (P<0.05) in control pigs and returned to baseline levels within 60 min. HED pigs were hyperglycemic at time 0, and blood glucose did not return to baseline (P = 0.01), even 4 h post-challenge. During OGTT, glucose area under the curve (AUC) was higher and insulin AUC was lower in HED pigs compared to controls (P = 0.001). Chronic HED intake increased (P<0.05) subcutaneous, intramuscular, and perirenal fat deposition, and induced hyperglycemia, hypoinsulinemia, and low-density lipoprotein hypercholesterolemia. A subset of HED pigs (n = 7) was transitioned back to a control diet for an additional six weeks. These pigs were subjected to an additional OGTT at 22 wk. Glucose AUC and insulin AUC did not improve, supporting that dietary intervention was not sufficient to recover glucose tolerance or insulin production. These data suggest a HED may be used to increase adiposity and disrupt glucose homeostasis in young, growing pigs.

The young Göttingen minipig as a model of childhood and adolescent obesity: influence of diet and gender

OBJECTIVE

Gender and sex hormones influence the development of obesity and metabolic syndrome in humans and Göttingen minipigs. The aim of this study was to investigate possible gender differences in the metabolic response to a high energy diet in young Göttingen minipigs as a model of childhood/adolescent obesity.

DESIGN AND METHODS

Nine-week-old male and female Göttingen minipigs were fed restrictedly on either a low energy diet (LED) or a high energy diet (HED) for 4 months (n = 5-7). Parameters of interest were fat percentage, visceral fat mass, plasma lipids and glucose tolerance, insulin resistance, and β-cell function measured by oral and intravenous glucose tolerance tests.

RESULTS

At 11 to 12 weeks of age, after 2 weeks diet feeding, both genders on HED had increased fat percentage, glucose intolerance, decreased insulin sensitivity, and increased plasma levels of cholesterol and triglycerides (TGs). There was no gender difference in body weight (BW) or fat percentage, but males had lower glucose tolerance than females. After 3.5 to 4 months on the diets, the pigs on HED had increased BW, fat percentage, and visceral fat mass and were more glucose intolerant and insulin resistant than pigs on LED. Also increases in plasma cholesterol and TG levels were observed in the pigs on HED. Females had higher fat percentage and more visceral fat, were more insulin resistant, and had a more unfavorable lipid profile compared with males independent of diet.

CONCLUSION

In conclusion, the young Göttingen minipig, and especially the female gender, seems to be a potential model for diet induced childhood/adolescent obesity and metabolic syndrome.

Co-methylated genes in different adipose depots of pig are associated with metabolic, inflammatory and immune processes

It is well established that the metabolic risk factors of obesity and its comorbidities are more attributed to adipose tissue distribution rather than total adipose mass. Since emerging evidence suggests that epigenetic regulation plays an important role in the aetiology of obesity, we conducted a genome-wide methylation analysis on eight different adipose depots of three pig breeds living within comparable environments but displaying distinct fat level using methylated DNA immunoprecipitation sequencing. We aimed to investigate the systematic association between anatomical location-specific DNA methylation status of different adipose depots and obesity-related phenotypes. We show here that compared to subcutaneous adipose tissues which primarily modulate metabolic indicators, visceral adipose tissues and intermuscular adipose tissue, which are the metabolic risk factors of obesity, are primarily associated with impaired inflammatory and immune responses. This study presents epigenetic evidence for functionally relevant methylation differences between different adipose depots.

Glucose tolerance is affected by visceral adiposity and sex, but not birth weight, in Yucatan miniature pigs

Epidemiological studies have linked small birth weight and lack of breastfeeding to type 2 diabetes mellitus. This study aimed to determine if (i) small birth weight promotes and (ii) suckling prevents the development of adiposity and diabetes biomarkers in a Yucatan miniature pig model. At 3 days of age, the intrauterine growth-restricted (IUGR) piglet (n = 6) was paired with a normal weight (NW), same-sex littermate (n = 6) and fed milk replacer for 4 weeks. A sow-fed normal weight littermate (n = 6) was also compared with the NW littermate to assess the effects of suckling. All pigs were fed a standard diet ad libitum for 5 h·day–1 from week 4. At 9.5 months, pigs underwent intravenous glucose tolerance (IVGTT) and insulin sensitivity tests (IST). At 10 months, tissues were harvested for fat analysis and pancreas histology. IUGR pigs demonstrated compensatory growth before sexual maturity and had greater subcutaneous fat depth; birth weight also negatively correlated with visceral fat content. Visceral and subcutaneous adiposity were greater in females than males. IVGTT and IST outcomes were not different due to birth weight or suckling. However, visceral adiposity was associated with several glucose tolerance outcomes and females were more glucose intolerant due to their greater adiposity. Pancreas insulin content or histology outcomes were not different. This model did not develop markers of type 2 diabetes mellitus because of small birth weight or formula feeding. However, visceral adiposity and sex were associated with glucose intolerance, which is consistent with data in humans.

Dietary monounsaturated fat in early life regulates IGFBP2: implications for fat mass accretion and insulin sensitivity

The aim of this study was to investigate effects of dietary supplementation with fat or sugar on body composition (BC) and insulin sensitivity (IS) in maturing pigs. Fifty newborn pigs randomized to a control diet or 18% saturated fat (SF), 18% monounsaturated fat (MUF), 18% mixed fat (MF), or 50% sucrose (SUC), from 1 to 16 weeks of age. Outcomes included weight gain, BC (dual energy X-ray absorptiometry, DXA), IS (fasting insulin and hyperinsulinaemic-euglycaemic clamps), fasting Non-Esterified Fatty Acid (NEFA) concentrations, and mRNA expression of genes involved in lipogenesis and IS in skeletal muscle (SM), subcutaneous (SAT), and visceral adipose tissue (VAT). In vitro studies examined direct effects of fatty acids on insulin-like growth factor-binding protein 2 (IGFBP2) mRNA in C2C12 myotubes. While SUC-fed pigs gained most weight (due to larger quantities consumed; P < 0.01), those fed fat-enriched diets exhibited more weight gain per unit energy intake (P < 0.001). Total (P = 0.03) and visceral (P = 0.04) adiposity were greatest in MUF-fed pigs. Whole-body IS was decreased in those fed fat (P = 0.04), with fasting insulin increased in MUF-fed pigs (P = 0.03). SM IGFBP2 mRNA was increased in MUF-fed pigs (P = 0.009) and, in all animals, SM IGFBP2 mRNA correlated with total (P = 0.007) and visceral (P = 0.001) fat, fasting insulin (r = 0.321; P = 0.03) and change in NEFA concentrations (r = 0.285; P = 0.047). Furthermore, exposure of in vitro cultured myotubes to MUF, but not SF, reduced IGFBP2 mRNA suggesting a converse direct effect. In conclusion, diets high in fat, but not sugar, promote visceral adiposity and insulin resistance in maturing pigs, with evidence that fatty acids have direct and indirect effects on IGFBP2 mRNA expression in muscle.

MicroRNAs miR-27a and miR-143 regulate porcine adipocyte lipid metabolism

MicroRNAs (miRNAs) are non-coding small RNAs that play roles in regulating gene expression. Some miRNAs have been classed as epigenetic regulators of metabolism and energy homeostasis. Previous reports indicated that the miRNAs miR-27a and miR-143 were involved in lipid metabolism in human and rodents. To determine the roles of porcine miR-27a and miR-143 in adipocyte lipid metabolism, porcine adipocytes were cultured and allowed to induce differentiation for 10 days. The lipid-filled adipocytes were then transfected with miRNA mimics and inhibitors. We measured how the indicators of adipogenesis and adipolysis in porcine adipocytes were affected by the over-expression and by the inhibition of both miR-27a and miR-143. The results indicated that the over-expression of miR-27a could accelerate adipolysis releasing significantly more glycerol and free fatty acids than the negative control (P < 0.001), while the mimic of miR-143 expression, promoted adipogenesis by accumulating more triglycerides (P < 0.001) in the adipocytes. In addition, we demonstrated that there was good correlation (r > 0.98, P < 0.001) between the indicators of adipolysis in cell lysates and in the culture medium.

Cannabinoid effects on CB1 receptor density in the adolescent brain: an autoradiographic study using the synthetic cannabinoid HU210

The short- and long-term behavioral effects of cannabinoids differ in adolescent and adult rodents. Few studies though have examined the underlying neurochemical changes that occur in the brain following adolescent cannabinoid exposure. In this study, we examined the effect of treatment with the synthetic cannabinoid, HU210, on CB1 receptor density in the brain and on body weight in adolescent male rats. Rats were treated daily with 25, 50, or 100 μg/kg HU210 for 4 or 14 days, or received a single dose of 100 μg/kg HU210 and sacrificed 24 h later. Receptor density was investigated using in vitro autoradiography with the CB1 receptor ligand [(3)H] CP55,940. In contrast to adult animals treated under the same paradigm in a previous study, adolescents continued on average, to gain weight over the course of the study. Weight gain was slowest in the 100 μg/kg group and improved dose dependently with controls gaining the most weight. Following the acute dose of HU210, a trend for a reduction in [(3)H] CP55,940 binding and a significant effect of treatment was observed. Statistically significant, dose-dependent, region-specific decreases in binding were observed in all brain regions examined following 4 and 14 days treatment. The pattern of CB1 receptor downregulation was similar to that observed in adults treated with cannabinoids in previous studies; however, its magnitude was smaller in adolescents. This reduced compensatory response may contribute to some acute behavioral effects, the pharmacological cross-tolerance and the long-lasting, adverse psychological consequences of cannabinoid exposure during adolescence.

Effects of deoxynivalenol consumption on body weight and adiposity in the diet-induced obese mouse

The potential for the obese state to alter sensitivity to toxic chemicals is poorly understood. In this study, dose-response effects of the trichothecene deoxynivalenol (DON), a common food-borne mycotoxin, were determined on body weight of diet-induced obese mice. In study 1, the effects of feeding adult female B6C3F1 mice a high-fat diet (HFD; 60% kcal from fat) containing 0, 2, 5, or 10 ppm DON for 10 wk on body weight and adiposity were compared. Mice consuming 5 or 10 ppm DON exhibited a 15 and 24% decrease in weight gain and a 50 and 83% reduction in periuterine fat, respectively. In study 2, mice were fed HFD for 8 wk to induce obesity and the effects of consuming HFD + 0, 2, 5, or 10 ppm DON for 8 wk were then determined. Mice fed 5 or 10 ppm DON exhibited a 16 and 23% weight reduction and a 0 and 40% periuterine fat reduction, respectively. In a follow-up experiment, food consumption was measured prior to and after the transition from HFD to HFD + 10 ppm DON. Exposure to DON was found to lower HFD consumption within 1 d, with significant weight loss in DON-fed mice evident after 6 d. In both studies 1 and 2, consumption of 5 or 10 ppm DON diminished circulating levels of insulin-like growth factor acid-labile subunit. Taken together, DON consumption lowered weight gain and produced weight loss in diet-induced obese mice at higher thresholds than that observed previously in normal B6C3F1 mice.

The effect of skeletal maturity on the regenerative function of intrinsic ACL cells

Anterior cruciate ligament (ACL) injuries are an important clinical problem, particularly for adolescent patients. The effect of skeletal maturity on the potential for ACL healing is as yet unknown. In this study, we hypothesized that fibroblastic cells from the ACLs of skeletally immature animals would proliferate and migrate more quickly than cells from adolescent and adult animals. ACL tissue from skeletally immature, adolescent, and adult pigs and sheep were obtained and cells obtained using explant culture. Cell proliferation within a collagen-platelet scaffold was measured at days 2, 7, and 14 of culture using AM MTT assay. Cellular migration was measured at 4 and 24 h using a modified Boyden chamber assay, and cell outgrowth from the explants also measured at 1 week. ACL cells from skeletally immature animals had higher proliferation between 7 and 14 days (p<0.01 for all comparisons) and higher migration potential at all time points in both species (p<0.01 for all comparisons). ACL cells from skeletally immature animals have greater cellular proliferation and migration potential than cells from adolescent or adult animals. These experiments suggest that skeletal maturity may influence the biologic repair capacity of intrinsic ACL cells.

Influence of prenatal nutrition and obesity on tissue specific fat mass and obesity-associated (FTO) gene expression

The recent discovery of an association between body composition, energy intake and the fat mass and obesity-associated (FTO) gene represents a promising new therapeutic target in obesity prevention. In a well, pre-established large animal model, we investigated the regulation ofFTOgene expression under conditions either leading to obesity or increased risk of obesity related disorders: i) a sedentary ‘Western’ lifestyle and ii) prenatal exposure to nutrient restriction. Pregnant sheep were either fed to fully meet their nutritional requirements throughout gestation or 50% of this amount from early-to-mid gestation. Following weaning, offspring were either made obese through exposure to a sedentary obesogenic environment or remained lean. A significant positive relationship between placentalFTOgene expression and fetal weight was found at 110 days gestation. In both the newborn and adult offspring, the hypothalamus was the major site ofFTOgene expression. HypothalamicFTOgene expression was upregulated by obesity and was further increased by prenatal nutrient restriction. Importantly, we found a strong negative relationship between the hypothalamicFTOgene expression and food intake in lean animals only that may imply FTO as a novel controller of energy intake. In contrast,FTOgene expression in the heart was downregulated in obese offspring born to nutrient restricted mothers. In addition,FTOgene expression was unaffected by obesity or prenatal diet in insulin-dependent tissues, where it changed with age possibly reflecting adaptations in cellular energetic activity. These findings extend information gained from human epidemiology and provide new insights into the regulation ofin vivoenergy metabolism to prevent obesity.

Influence of birth weight on gene regulators of lipid metabolism and utilization in subcutaneous adipose tissue and skeletal muscle of neonatal pigs

Epidemiological studies suggest that low-birth weight infants show poor neonatal growth and increased susceptibility to metabolic syndrome, in particular, obesity and diabetes. Adipose tissue development is regulated by many genes, including members of the peroxisome proliferator-activated receptor (PPAR) and the fatty acid-binding protein (FABP) families. The aim of this study was to determine the influence of birth weight on key adipose and skeletal muscle tissue regulating genes. Piglets from 11 litters were ranked according to birth weight and 3 from each litter assigned to small, normal, or large-birth weight groups. Tissue samples were collected on day 7 or 14. Plasma metabolite concentrations and the expression ofPPARG2,PPARA,FABP3, andFABP4genes were determined in subcutaneous adipose tissue and skeletal muscle. Adipocyte number and area were determined histologically. Expression ofFABP3and4was significantly reduced in small and large, compared with normal, piglets in adipose tissue on day 7 and in skeletal muscle on day 14. On day 7,PPARAandPPARG2were significantly reduced in adipose tissue from small and large piglets. Adipose tissue from small piglets contained more adipocytes than normal or large piglets. Birth weight had no effect on adipose tissue and skeletal muscle lipid content. Low-birth weight is associated with tissue-specific and time-dependent effects on lipid-regulating genes as well as morphological changes in adipose tissue. It remains to be seen whether these developmental changes alter an individual's susceptibility to metabolic syndrome.

Evaluation of different methods for assessment of insulin sensitivity in Gottingen minipigs: introduction of a new, simpler method

The use of animal models in diabetes research requires reliable tests for evaluation of insulin sensitivity and beta-cell function. Minipigs are being increasingly used in metabolic research, and the aim of this study was to compare different tests and indexes for evaluation of insulin sensitivity and beta-cell function in Göttingen minipigs. Hyperinsulinemic, isoglycemic clamp, intravenous (IVGTT) and oral glucose tolerance tests (OGTT), and a modified insulin tolerance test were performed in minipigs fed either low- or high-energy diet. Furthermore, the reproducibility of IVGTT-derived parameters was assessed. Previously described insulin sensitivity indexes [steady-state glucose infusion rate/glucose concentration/insulin concentration from clamp (M/G/I); oral glucose insulin sensitivity (OGIS) and ISI(comp) from OGTT; S(I) from minimal model analysis of IVGTT; and quantitative insulin sensitivity check index from fasting values] were calculated together with an insulin sensitivity index from the modified insulin tolerance test (ISI(ITT)) and a new simple index (S2) derived from the first 30 min of the IVGTT. beta-Cell function was assessed from the IVGTT and the OGTT. Reproducibility of the IVGTT-derived parameters was calculated as median intraindividual coefficient of variation (CV%).M/G/I correlated significantly only with S2 (P < 0.05, r = 0.54). S2 furthermore correlated with S(I) (P < 0.001, r = 0.81), ISI(ITT) (P < 0.001, r = 0.57), and the two indexes from OGTT, ISI(comp) (P < 0.001, r = 0.78) and OGIS (p < 0.05, r = 0.48). No correlation was found between beta-cell function indexes from OGTT and IVGTT. The median CV% of the new S2 index was 13. In conclusion, the new simple index of insulin sensitivity, S2, was revealed to be useful for evaluation of insulin sensitivity in pigs.

Patterns of gene expression in pig adipose tissue: insulin-like growth factor system proteins, neuropeptide Y (NPY), NPY receptors, neurotrophic factors and other secreted factors

Although cDNA microarray studies have examined gene expression in human and rodent adipose tissue, only one microarray study of adipose tissue from growing pigs has been reported. Total RNA was collected at slaughter from outer subcutaneous adipose tissue (OSQ) and middle subcutaneous adipose tissue (MSQ) from gilts at 90, 150, and 210 d (n=5 age(-1)). Dye labeled cDNA probes were hybridized to custom porcine microarrays (70-mer oligonucleotides). Gene expression of insulin-like growth factor binding proteins (IGFBPs), hormones, growth factors, neuropeptide Y (NPY) receptors (NPYRs) and other receptors in OSQ and MSQ changed little with age in growing pigs. Distinct patterns of relative gene expression were evident within NPYR and IGFBP family members in adipose tissue from growing pigs. Relative gene expression levels of NPY2R, NPY4R and angiopoietin 2 (ANG-2) distinguished OSQ and MSQ depots in growing pigs. We demonstrated, for the first time, the expression of IGFBP-7, IGFBP-5, NPY1R, NPY2R, NPY, connective tissue growth factor (CTGF), brain-derived neurotrophic factor (BDNF) and ciliary neurotrophic factor (CNTF) genes in pig adipose tissue with microarray and RT-PCR assays. Furthermore, adipose tissue CTGF gene expression was upregulated while NPY and NPY2R gene expression were significantly down regulated by age. These studies demonstrate that expression of neuropeptides and neurotrophic factors in pig adipose tissue may be involved in regulation of leptin secretion. Many other regulatory factors were not influenced by age in growing pigs but may be influenced by location or depot.

Evaluation of beta-cell mass and function in the Göttingen minipig

Increased knowledge about beta-cell mass and function is important for our understanding of the pathophysiology of type 2 diabetes (T2DM). The relationship between the two is difficult to study in humans, whereas animal models allow studies of consequences of, for example, reduction of beta-cell mass and induction of obesity and procurement of the pancreas for histological examination. An overview of results obtained in the Göttingen minipig in relation to beta-cell function, and mass is provided here. Effects of a primary reduction of beta-cell mass have indicated that not all of the defects of pulsatile insulin secretion in human T2DM can be explained by reduced beta-cell mass. Furthermore, induction of obesity has shown deterioration of beta-cell function and morphological changes in the pancreas. As in humans, obesity leads to an increased beta-cell volume in the minipig, and based on the increased number of islets, neogenesis of islets is an important factor in expansion of beta-cell mass in this species. Measurement of beta-cell function as an estimate of beta-cell mass is, at present, the only method possible in humans, and this approach has been validated using lean and obese minipigs with a range of beta-cell mass. The effects on beta-cell function and mass of obesity of longer duration and/or more pronounced hyperglycaemia remains to be determined, but the models developed so far represent a valuable tool for such investigations.

Patterns of gene expression in pig adipose tissue: Transforming growth factors, interferons, interleukins, and apolipoproteins1

Although cDNA microarray studies have indicated the expression of unique and unexpected genes and their products in human and rodent adipose tissue, cDNA microarray studies of adipose tissue from growing pigs have not been reported. Total RNA was collected at slaughter from outer s.c. adipose tissue (OSQ), middle s.c. adipose tissue (MSQ), ovary, uterus, hypothalamus, and pituitary tissue samples from gilts at 90, 150, and 210 d (n = 5/age). Dye-labeled cDNA probes were hybridized to custom microarrays (70 mer oligonucleotides) representing approximately 600 pig genes involved in growth and reproduction. Expression intensity ratios revealed little change in expression of 27 cytokines and 4 apolipoproteins with age in OSQ and MSQ from pigs at 90, 150, and 210 d of age. Distinct patterns of relative gene expression were evident within apolipoproteins, IL, interferons, and transforming growth factor beta family members in adipose tissue from growing pigs (90-, 150-, and 210-d-old pigs). Patterns of gene expression within apolipoproteins, IL, interferons, and transforming growth factor beta family members distinguished OSQ and MSQ depots in growing pigs. We also demonstrated, for the first time, the expression of several major cytokine and apolipoprotein genes in pig adipose tissue, including small inducible cytokine A5 (RANTES), IL-1B, IL-1A, IL-12A, IL-1 receptor antagonist, and apolipoproteins A1 and E with microarray and reverse transcription-PCR assays or reverse transcription-PCR assays alone. These studies demonstrate that expression of major cytokine and apolipoprotein genes in pig adipose tissue are not influenced by age in growing pigs but may be influenced by location or depot.

Cellular and biochemical features of skeletal muscle in obese Yucatan minipigs

OBJECTIVE

To examine cellular and biochemical features of skeletal muscle in response to dietary-induced obesity in a novel Yucatan minipig model of childhood obesity.

RESEARCH METHODS AND PROCEDURES

From 4 to 16 months of age, minipigs were fed either a recommended human-type diet (NF; n = 4) or were overfed a western-type diet with saturated fat and high-glycemic index carbohydrates (OF, n = 4). Muscle samples (biceps femoris) were histochemically stained for the identification of intramuscular adipocytes, intramyocellular lipid aggregates (oil red O), and myofiber types (myosin ATPase, succinate dehydrogenase). Gene expressions and/or activities of factors involved in lipogenesis, lipolysis, or energetic metabolism were quantified in muscle.

RESULTS

Cross-sectional areas of myofibers paralleled pig body weight (r = 0.86, p < 0.01). The size of intramuscular adipocytes, the relative proportion of oil red O-stained fibers, and total muscle lipid content tended (p < or = 0.10) to increase in response to OF diet. Hormone-sensitive lipase, carnitine palmityl transferase-I, and uncoupling protein 2 mRNA levels were lower (p < 0.05) in OF pigs than in NF pigs. Activities of beta-hydroxyacyl-coenzyme A dehydrogenase and citrate synthase assessing post-carnitine palmityl transferase I events and the proportion of oxidative myofibers were not altered by OF diet. Activity and gene expression of fatty acid synthase were lower (p < 0.02) in OF pigs than in NF pigs.

DISCUSSION

Overfeeding in Yucatan minipigs reduced the expression levels of three catabolic steps in skeletal muscle that are involved also in the etiology of human obesity.