Insulin kinetics in juvenile canine diabetics after glucose loading

Glucose and insulin kinetics were studied in 4 juvenile canine diabetics and 6 healthy controls. Diabetic dogs were glucose intolerant with delayed insulin response after glucose challenge. Total insulin secretion was near that of the controls, but was inadequate when compared with corresponding plasma glucose concentrations.     

Insulin response to glucose in estrous and diestrous obese and lean heifers

This study determined if the insulin and glucose responses to glucose infusion in obese (n = 4) and lean (n = 4) Holstein heifers were affected by stage of the estrous cycle. Glucose (.35 g/kg) was infused within 2 min into the jugular veins of heifers during diestrus (d 15) and at the subsequent estrus (d 0). Concentrations of insulin and glucose were determined in jugular venous serum obtained from blood samples collected at 60, 45, 30, 15 and 1 min before and at 2.5, 5, 10, 15, 20, 30, 40, 50, 60, 80, 100, 120, 140, 160, 180, 210 and 240 min after glucose. Mean (+/- SE) pretreatment concentrations of glucose (mg/100 ml) in obese (68 +/- 1.9) and lean (71 +/- 2.5) heifers were unaffected by body condition and stage of the cycle. Mean (+/- SE) pretreatment concentrations of insulin (microU/ml) were unaffected by stage of the cycle but were higher (P less than .05) in obese (33 +/- 3.6) than in lean (18 +/- 2.7) heifers. Body condition affected the insulin response with greater absolute concentrations (P less than .01) and total (P less than .005) response areas of insulin in obese than in lean heifers. Kinetics of the injected glucose were unaffected by body condition and stage of the cycle.(ABSTRACT TRUNCATED AT 250 WORDS)     

Insulin regulation of leptin expression in streptozotocin diabetic pigs

The relationship between leptin mRNA and insulin status was explored using streptozotocin diabetic pigs. Twelve male Yorkshire x Landrace crossbred swine (approximately 40 kg BW) were divided into three groups. Two groups were rendered diabetic with the use of streptozotocin (75 mg/kg BW). Diabetes was confirmed 24 h after streptozotocin treatment by the presence of hyperglycemia. One group of diabetic animals received daily injections of insulin (.5 U/(kg x d)(-1)) for 7 d, whereas the other group of diabetic animals received saline injections. The nondiabetic group also received saline injections (controls). Tissue and blood were collected after 7 d of treatment. Leptin mRNA concentrations in dorsal s.c. adipose tissue were measured by Northern analysis and standardized against 28S rRNA expression. Diabetes reduced leptin mRNA concentration by 67% in s.c. adipose tissue (P < .05). Serum insulin concentrations in the diabetic animals were reduced by 69% (P < .05). Insulin treatment of diabetic animals resulted in an increase in leptin mRNA concentration to levels in controls. Primary cell culture of porcine adipose tissue was used to assess whether these actions were the direct or indirect action of insulin. Acute exposure (1 to 24 h) of primary cultures of porcine adipocytes to insulin did not result in a change in leptin expression. However, chronic (7-d) exposure to insulin elevated leptin mRNA levels by 73%. These data suggest that insulin mediates changes in porcine leptin mRNA levels in vivo or in vitro, most likely by an indirect action.     

Insulin and growth hormone responses to glucose infusion in mature and first-lactation dairy cows

Five mature Holstein cows and 6 first-lactation Holstein cows were administered 100 mg of glucose/kg of body weight, IV, over a 20-minute period on postpartum day 30. A series (preinfusion, glucose infusion, and postinfusion) of blood samples was collected at -15, -10, -5, 5, 10, 15, 20, 30, 45, 60, 75, 90, 105, and 120 minutes from the start of the infusion. Serum was obtained and was assayed for glucose, immunoreactive insulin (IRI), growth hormone (GH), and free fatty acid concentrations. Baseline glucose and free fatty acid concentrations were similar in cattle of both groups throughout the sample collection period. Both groups of cattle disposed of the infused glucose in a similar manner. The first-lactation cows secreted significantly (P less than 0.0001) more IRI to utilize the glucose load than did the mature cows, 71 +/- 13 microU/ml vs 38 +/- 7 microU/ml, respectively (mean +/- SEM). Preinfusion and glucose infusion GH concentrations were similar in cattle of both groups. In the postinfusion period, GH values were significantly (P less than 0.0002) higher in the first-lactation cows (8.7 +/- 1.8 ng/ml) than in the mature cows (5.8 +/- 1.6 ng/ml). Compared with that in the mature cows, the higher IRI concentration required by the first-lactation cows to utilize approximately the same glucose load suggested that first-lactation cows were insulin resistant. The increased insulin response to increased glucose concentration may be one reason first-lactation cows produce less milk than do mature cows. Other factors, such as variation in the ability of the mammary gland to synthesize milk cannot be excluded.     

Nonruminant Nutrition Symposium: intestinal glucose sensing and regulation of glucose absorption: implications for swine nutrition

The Na(+/)glucose cotransporter (SGLT1) is the major route for the transport of dietary sugars from the lumen of the intestine into enterocytes. Regulation of this protein is essential for the provision of glucose to the body and avoidance of intestinal malabsorption. This has important nutritional implications in particular for young and growing animals. It has been demonstrated that dietary sugars and artificial sweeteners increase SGLT1 expression and the capacity of the gut to absorb monosaccharides. Furthermore, diets supplemented with artificial sweeteners have been shown to improve growth and performance of weaning piglets. In this review, after describing the organization of intestinal epithelium, the type of gut hormones released in response to dietary carbohydrates, the mechanism underlying the transcellular transport of glucose in the intestine is outlined. Next, a historical background to the work carried out in various laboratories aimed at identifying molecular mechanisms involved in regulation of intestinal glucose transporter, SGLT1, is described. Subsequently, the more recent data on the role of intestinal glucose, or sweet, sensor T1R2 + T1R3, a G protein-coupled receptor, required for upregulation of SGLT1 by dietary sugars and artificial sweeteners, are presented. The glucose sensor subunits, T1R2 + T1R3, are members of the taste receptor family 1, T1R, and are expressed in the gut enteroendocrine cells. Sensing of dietary sugars and artificial sweeteners by T1R2 + T1R3 activates a pathway in endocrine cells leading to secretion of gut hormones. Finally, after describing molecular mechanisms by which a specific gut hormone released by endocrine cells may regulate SGLT1 expression in the neighboring absorptive enterocytes, the application of these findings to enhancing intestinal capacity to absorb dietary sugars in weaning piglets is presented. A better understanding of the molecular events involved in regulation of SGLT1 will allow the identification of nutritional targets with attendant promise of avoiding nutrient malabsorption and enhancing growth and well-being of species.     

Neuroendocrine regulation of growth hormone secretion in sheep. II. Effect of somatostatin on growth hormone and glucose levels.

The effect of intravenous (iv) and intracerebroventricular (icv) administration of somatostatin on the plasma levels of growth hormone (GH) and glucose was studied in sheep. Intravenous somatostatin decreased (P less than 0.001) circulating GH when infused at the rate of 5 micrograms/min (150 ng/kg/min) over 1 hr, but when used at 1 microgram/min there was no effect on plasma GH levels during infusion. At both doses used there was an indication of an increase in GH following the cessation of somatostatin infusion. Somatostatin given at both these doses iv had no effect on plasma glucose levels. When given icv neither 1.8 micrograms, 18 micrograms nor 180 micrograms somatostatin had any significant effect of plasma GH levels, although there was a significant (P less than 0.05) elevation in GH levels 75 min after 180 micrograms somatostatin icv. Plasma glucose levels did not increase following injection of somatostatin icv at 1.8 or 18 micrograms, but there was a clear hyperglycaemic episode following 180 micrograms icv. Despite a lack of effect of somatostatin on GH release when given icv, there was a clear elevation (P less than 0.05) in plasma GH levels immediately following icv administration of a somatostatin antiserum. These data indicate that iv administration of somatostatin at pharmacological levels can depress unstimulated GH levels in sheep while administration icv does not. Central administration of somatostatin increases plasma glucose levels only at high doses and seems unlikely to be of physiological importance in glucose homeostasis.     

骨骼肌撞代谢及其调控的研究进展

骨骼肌糖代谢是动物骨骼肌蛋白质和肌内脂肪合成以及肌肉活动的重要能量来源,其代谢速度和程度对最终肉质形成发挥重要的作用.文章结合近年来的文献报道和本试验室的研究结果系统综述了骨骼肌糖代谢的过程、组织学基础、分子学基础及其调控机制,为从分子水平系统深入开展骨骼肌糖代谢调控研究提供参考.     

奶牛围产期葡萄糖营养平衡及其调控研究进展

奶牛围产后期干物质采食量(DMI)下降明显,处于能量负平衡(NEB)状态,机体通过动员体脂满足胎儿、启动泌乳及维持的能量需要,其饲养管理关系到整个泌乳期的成败。脂类饲料中的不饱和脂肪酸(UFA)易被氧化,通过增加脂类提高日粮能量浓度会加剧奶牛氧化应激。葡萄糖是反刍动物的重要能量来源,不仅参与细胞能量代谢过程,而且还是乳腺合成乳糖的前体物质,源于内源生成和肠道吸收。运用营养调控技术促进葡萄糖摄取,提高机体可利用葡萄糖水平,是解决NEB问题和降低氧化应激的有效策略。文章总结了反刍动物机体葡萄糖的来源及影响葡萄糖吸收的因素,并探讨提高围产期奶牛可利用葡萄糖水平的技术方案,以期为葡萄糖的合理供应提供依据。     

Insulin responsiveness to glucose and tissue responsiveness to insulin over the feeding cycle in sheep

Insulin responsiveness to glucose and tissue responsiveness to insulin, using the hyperglycemic clamp and the hyperinsulinemic euglycemic clamp techniques, were measured before, during and after feeding in sheep fed an alfalfa hay and commercial concentrate diet. Glucose infusion rate and the plasma insulin increment in the hyperglycemic clamp experiment were higher during the feeding period (0 to 1 h after initiating feeding) than during the pre- and post-feeding periods. The ratio of plasma insulin increment to glucose infusion rate remained unchanged over the feeding cycle. Only a slight increase (P less than .05) in the glucose infusion rate was observed during feeding in the hyperinsulinemic euglycemic clamp experiment. These results suggest that insulin responsiveness to glucose tends to be enhanced during the feeding period but that tissue responsiveness to insulin is not changed over the feeding cycle in sheep.     

Insulin sensitivity and glucose dynamics during pre-weaning foal development and in response to maternal diet composition

Nutritional management of animals during pregnancy can affect glucose and insulin dynamics in the resulting offspring through influences on fetal development. Additionally, high starch feeding in mature horses is associated with reduced insulin sensitivity and an increased risk for diseases such as obesity and laminitis. However, no study has yet evaluated the effect of feeding a high starch diet to pregnant mares on glucose and insulin dynamics in their offspring. Twenty late-gestation mares maintained on pasture were provided two-thirds of digestible energy requirements from isocaloric, isonitrogenous low starch (LS, n = 10) or high starch (HS, n = 10) feed. Their foals were assessed with an insulin-modified frequently sampled intravenous glucose tolerance test at 5, 40, 80, and 160 d of age. Baseline glucose concentrations, insulin sensitivity, and insulin-independent glucose clearance in 5-d foals were all greater than values observed in mature horses and declined towards mature values as foals reached 160 d of age. Baseline glucose concentrations were all within normal range, but higher in foals born from HS mares through 80 d of age. Insulin sensitivity was not different between dietary groups until a trend for lower insulin sensitivity in HS foals emerged at 160 d of age. These data are the first to characterize decreasing insulin sensitivity and glucose tolerance in Thoroughbred foals from 5 to 160 d of age. This study also presents the first data examining glucose and insulin dynamics in developing foals in response to maternal high starch diet.     

Evaluation of blood glucose concentration during exertion. 6. Effect of anemia on the glucose regulation capacity of domestic swine in standardized running exercise]

Individual mean blood glucose values and the scatter of individual values were determined in six healthy and six anaemic pigs before, during and after ten minutes of exercise on a belt moving at 78 m/min (environmental temperature 22-24 degrees C, relative humidity 55-65%). The glucose regulatory capacity of anaemic pigs was inferior to that of healthy pigs. Blood glucose regulation was related to haemoglobin content and to the increase in rectal temperature during exercise.     

Insulin therapy for dogs and cats.

Management of diabetic dogs and cats requires a tremendous cooperative effort between the practitioner and the client. Consistency in the handling, availability, and formulations of the different insulins will improve client compliance. In addition to insulin therapy, successful management of the diabetic animal includes the client's perceptions of the animal's health, maintenance of the animal's body weight, consistency in water consumption, and monitoring serial blood glucose concentrations. Serial blood glucose determinations improve the practitioner's ability to identify and address problems associated with insulin therapy, and thereby delay or minimize the complications of long-term diabetes.     

Insulin tolerance in laminitic ponies.

Sensitivity to insulin was assessed in ponies episodically affected with chronic laminitis by measurement of blood glucose and arterial blood pressure during insulin tolerance tests. In terms of blood glucose values, laminitic ponies were significantly less sensitive to insulin than controls. Conversely, a post-insulin decline in diastolic, systolic and mean blood pressure values was significantly greater in laminitic ponies than in controls.