Equine Metabolic Syndrome

Equine metabolic syndrome (EMS) is important because of its association with laminitis. Obesity and insulin resistance are two important components of EMS, and the underlying cause of this syndrome is likely to be enhanced metabolic efficiency. Affected horses are often referred to as “easy keepers” because they require fewer calories to maintain body condition, and enhanced metabolic efficiency is an inherent risk factor for EMS that may be genetically determined. Pony breeds, Morgan horses, and Paso Finos are predisposed to EMS, but this problem can be prevented through effective management. Overfeeding, abundant pasture grass, and inadequate exercise are risk factors that relate to modern management practices. Obesity and adiposity induce insulin resistance, and recent research suggests that this is the determinant of laminitis susceptibility in ponies. Increased plasma insulin concentrations are detected in most affected horses and ponies, so this serves as a useful screening test for EMS. Physical characteristics also should be examined because horses with EMS exhibit regional adiposity in the form of a cresty neck or abnormal adipose tissue deposits close to the tailhead. All horses with enhanced metabolic efficiency, obesity, or regional adiposity should be screened for EMS. The combined intravenous glucose−insulin test can be performed to diagnose insulin resistance in mildly affected horses and quantify insulin sensitivity. Most horses with EMS can be effectively managed by reducing caloric intake, decreasing the starch and sugar content of the diet, increasing exercise, and limiting or eliminating access to pasture, but medical therapy is warranted in select cases.     

Effects of novel vaccines on weight loss in diet-induced-obese (DIO) mice

The purpose of the study was to test the therapeutic effects of novel vaccines for reducing weight gain and increasing weight loss in diet induced obesity (DIO) model. Male C57BL/6 J mice, fed a 60% Kcal fat diet for 8 weeks prior to the start of the study, were vaccinated via the intraperitoneal route with two formulations (JH17 & JH18) of chimeric-somatostatin vaccines at 1 and 22 days of the study. Control mice were injected with PBS. All mice continued to be feed the 60% Kcal fat diet for the 6 week study. Body weights were measured two times a week and food intake was measured weekly. At week 6, mice were euthanized and a terminal bleed was made and antibody levels to somatostatin and levels of insulin-like growth factor 1 (IGF-1) were determined. Vaccination with both vaccine formulations induced a statistically significant body weight change over the study period, as compared with PBS controls. Percentage of baseline body weight was also significantly affected by vaccination during the study period. Vaccinates finished the study at 104% and 107% of baseline weight, JH17 & JH18 respectively, while untreated controls reached 115% of baseline weight. Food intake per mouse was similar in all mouse groups during the entire study. Control mice did not demonstrate any antibody titers to somatostatin, while all vaccinated mice had measurable antibody responses (> 1:500,000 titer). IGF-1 levels were not statistically significant among the groups, but were elevated in the JH18 vaccinates (mean 440.4 ng/mL) when compared with PBS controls (mean 365.6 ng/mL). Vaccination with either JH17 or JH18 chimeric –somatostatin vaccines produced a statistically significant weight loss as compared with PBS controls (P < 0.0001), even though the DIO mice with continually fed a 60% Kcal fat diet. The weight loss/lower weight gain observations were even more significant, as all mice consumed similar amounts of food for the entire study. The presence of high levels of anti-somatostatin antibodies at 6 weeks was correlative with the weight observations and confirmed the success of vaccination.     

Activity and tissue-specific expression of lipases and tumor-necrosis factor alpha in lean and obese cats

Post-heparin plasma activity of lipoprotein lipase (LPL) and hepatic lipase (HL), and fat and muscle activity of LPL were measured in neutered lean and obese cats. Lipoprotein lipase, hormone-sensitive lipase (HSL), and tumor necrosis factor a (TNF) mRNA were measured in muscle and fat tissue with real-time PCR using primers for feline LPL, HSL, and TNF. Lipoprotein lipase plasma and fat activity and fat mRNA levels were significantly lower (50, 80, and 50%, respectively) in obese cats than lean cats, whereas the muscle/fat ratio of LPL was significantly higher in obese compared to lean cats. The activity of HL was not different between the groups. Hormone-sensitive lipase mRNA levels were significantly higher in obese than lean cats. The level of fat TNF also was significantly higher in obese cats than in lean cats, whereas the level in muscle was not different. The lower LPL activity and mRNA expression in fat and the higher LPL and HSL mRNA expression in muscle in obese cats compared to lean cats expectedly favor a redistribution of fatty acids from fat to muscle tissue where they can be deposited or used for energy in times of need. Tumor necrosis factor alpha may regulate this repartitioning process through suppression of adipocyte LPL.     

Intracerebroventricular Administration of Soy Protein Hydrolysates Reduces Body Weight without Affecting Food Intake in Rats

Some studies suggest that increased consumption of soy protein hydrolysates may cause body weight loss but the mechanism of action is unknown. The objective of this investigation was to determine whether intracerebroventricular (i.c.v.) infusion of soy protein hydrolysates decrease food intake and body weight. Adult male Sprague Dawley rats (n = 24) received i.c.v. injections of soy hydrolysate I (SH I) or soy hydrolysate II (SH II) three times weekly for 2 weeks. Krebs solution and leptin were used as negative and positive controls respectively. SH I (6.5–20 kDa with a strong band at 14 kDa) was produced by hydrolysis with alcalase, and SH II (∼2 kDa) was obtained by hydrolysis and ultrafiltration. Leptin successfully reduced body weight (−1.60 g) 24 h (p = 0.0093) after the third injection. SH I caused significant (p = 0.0009) decreases in body weight (−1.70 g) 24 h after the third injection but not after 48 h. SH II showed a tendency to prevent body weight gain but this effect was short of statistical significance (p < 0.40). Food intake was not affected by any of the soy hydrolysate treatments but leptin injection did cause significant decreases in food intake (p < 0.05). Data suggest that soy alcalase hydrolysate can decrease, in the short term, the rate of body weight gain independently of food consumption. This preliminary data show that soy peptides may play a role on body weight regulation, possibly by increasing energy utilization.     

Effect of breed on body composition and comparison between various methods to estimate body composition in dogs

The objectives of this clinical study were firstly, to assess the effects of breed/genetic group on body composition in dogs using Dual-X-ray absorptiometry (DEXA) as the reference method and secondly, to check, in clinical field conditions, if methods easy to apply in veterinary practice [bioelectrical impedance (BIA), morphometric equations, body condition score and body mass index] can give similar body composition results to DEXA results, using canine breeds with very different genetic and morphologic backgrounds. 19 dogs from 6 breeds with different genetic origin were used. Results showed that breed differences exist regarding body composition in dogs. Body condition score and morphometric equation should be developed by breed or by groups of breeds for an accurate estimation of body composition of the various breeds of dogs with a different genetic background or morphology. Any of the other tested methodologies (BIA or morphometric equations) gave results in agreement with DEXA value, when dogs with different genetic background and morphologic characteristics are used, but BIA, eventually in combination with morphometric measurements, could be a method to develop to estimate fat-free mass in dogs of different breeds.     

犬黑素皮质素受体-4裸质粒注射促进小鼠肥胖的研究

[目的]探讨犬黑素皮质素受体-4（MC4R）eDNA的重组真核表达质粒对小鼠肥胖的影响。[方法]3次尾静脉高压注射pcDNA3．1-myc．His／A-MCAR质粒,RT-PCR成功验证小鼠体内犬MC4R表达后,适时监测每只小鼠的体重,同窝小鼠相互对照,利用两两比较的秩和检验进行统计学分析。另外,用脂肪组织病理切片分析小鼠皮下脂肪细胞变化。[结果]试验得出,小鼠体重变化有统计学意义;饲养时间相同、相互对照组的每一组小鼠脂肪细胞直径对比明显,且具有统计学意义。[结论]犬MC4R基因在小鼠体内表达,能促进小鼠体重增加,为犬MC4R调节肥胖机制的研究提供理论依据。     

Insulin Sensitivity in Thoroughbred Geldings: Effect of Weight Gain,Diet, and Exercise on Insulin Sensitivity in Thoroughbred Geldings

The effects of dietary energy source, controlled weight gain, and exercise restriction on insulin sensitivity (SI) were studied in mature Thoroughbred geldings with body condition scores (BCS) of 4.3 ± 0.1. Two dietary energy sources were used, one high in starch and sugar (HS; n = 9) and one high in fat and fiber (HF; n = 7), and horses were fed 20 Mcal digestible energy (DE)/day above maintenance requirements to encourage weight gain. Using the minimal model of glucose and insulin dynamics, no differences in SI between groups were noted before initiation of treatment concentrate feeding. After dietary acclimation, SI was decreased in HS (P < 0.01) as compared with HF. After 32 weeks of controlled weight gain (90.8 kg; final BCS, 7.0 ± 0.1), SI remained lower in HS (P = 0.07) but did not change from the preweight gain value. SI in HF did not change between the start and end of weight gain. After completion of weight gain, exercise was restricted for 2 weeks, resulting in a reduction in SI in HF (P = 0.03) but no change in HS. It was concluded that dietary energy source may be more influential than weight gain on SI in the mature Thoroughbred gelding between BCS 4 and 7. The higher SI found in horses consuming the HF diet appeared to be partially dependent on some level of physical activity.     

Triiodothyronine differentially regulates key metabolic factors in lean and obese cats

The effect of a 2-week administration of 75microg triiodothyronine (T3) on substrate oxidation, heat production, non-esterified fatty acids, and leptin was evaluated in eight lean (three females and five males) and eight obese (five females and three males) age-matched adult neutered cats. In addition, using real-time RT-PCR, expression of muscle and adipose tissue uncoupling proteins (UCP2 and UCP3), deiodinase 1 and 2 (D1; D2), and peroxisome proliferator-activated receptor (PPAR) alpha and gamma and peroxisome-proliferator-activator receptor-gamma co-activator 1alpha (PGC1) was examined. Compared to lean cats, obese cats had increased NEFA, leptin, UCP2, and D1mRNA in muscle and UCP3mRNA levels in fat, but lower heat production, and fat PPARs and PGC1. T3 administration increased thermogenesis and NEFA in lean and obese cats, and adipose tissue PPARgamma in lean cats. It also increased muscle D1 in lean and D2 in obese cats. The increase in muscle D2 was interpreted to be reflective of the reduced serum total T4 concentration following T3 suppression of the pituitary. No effect was seen on leptin, or UCP2 and 3. This shows that T3 regulates thermogenesis but not through changes in uncoupling protein expression. It also indicates that PPARs have an important role in the pathogenesis of obesity in cats.