Time-action profiles of insulin detemir in normal and diabetic dogs

Insulin detemir is the first member of a new class of long-acting soluble insulin analogues capable of maintaining the basal level of insulin in humans. In this preliminary study, we investigated the time-action profiles of insulin detemir in normal and diabetic dogs since the use of insulin detemir in canines has yet to be determined. Eight animals were used in our study (three normal and five insulin dependent diabetic dogs). Time-action profiles of insulin detemir were monitored in normal dogs using an artificial pancreas apparatus under euglycemic condition. Blood sampling was performed at 2 h intervals post feeding, with insulin administration, in insulin dependent diabetic dogs. Time-action profiles of insulin detemir, in normal dogs, demonstrated that insulin detemir is a long-lasting preparation similar to what has been observed in humans. A pronounced peak was detected at 8–10 h while the glucose-lowering effect lasted for over 24 h after insulin injection, thus illustrating its longer prolonged peak activity time. Furthermore, intensive glycemic control was achieved with insulin detemir in insulin dependent diabetic dogs, using a lower dosage than NPH insulin and insulin glargine therapeutic doses. Our results indicate that insulin detemir has a greater effect than either NPH insulin or insulin glargine in canines, requiring a lower dose than either insulin preparation. However, using insulin detemir also carries a higher risk of inducing hypoglycemia as compared to either NPH insulin or insulin glargine.     

Clinical significance of plasma mannose concentrations in healthy and diabetic dogs

Circulating levels of monosaccharides can act as a reflection of systemic glucose/ energy metabolism. Characteristic changes observed in these levels can be seen in patients with diabetes and other metabolic disorders. There have been a few reports describing the significance of mannose metabolism as an energy source under physiological and pathological conditions. However, the relationship between circulating levels of mannose and the pathophysiology of diabetes mellitus are unknown in dogs. This study examined circulating levels of mannose between healthy control and diabetic dogs and evaluated the clinical significance of mannose levels in dogs. Diabetic dogs demonstrated a higher circulating level of mannose in comparison to normal healthy control dogs. Plasma mannose was positively correlated with plasma glucose and fructosamine, respectively. Interestingly, plasma mannose levels were affected by plasma insulin levels. In the context of feeding and glucose tolerance tests, plasma mannose levels responded to changes in circulating insulin levels. Circulating plasma mannose levels decreased after feeding in both control and diabetic animals in spite of observed insulin level differences. However, when glucose tolerance tests were given, a positive correlation between mannose levels and insulin levels was observed. Therefore, plasma mannose levels obtained via glucose tolerance testing may be used as a new diagnostic method for evaluating insulin resistance or deficiency in diabetic dogs.     

Oral chromium picolinate and control of glycemia in insulin-treated diabetic dogs

Chromium is an essential dietary trace mineral involved in carbohydrate and lipid metabolism. Chromium is required for cellular uptake of glucose, and chromium deficiency causes insulin resistance. Chromium supplementation may improve insulin sensitivity and has been used as adjunct treatment of diabetes mellitus in humans. In this study, 13 dogs with naturally acquired diabetes mellitus were treated with insulin for 3 months, then with insulin and chromium picolinate for 3 months. Dogs weighing <15 kg (33 lb: n = 9) were administered 200 microg of chromium picolinate PO once daily for I month, then 200 microg of chromium picolinate twice daily for 2 months. Dogs weighing >15 kg (n = 4) received 200 microg of chromium picolinate once daily for 2 weeks, then 200 microg twice daily for 2 weeks, then 400 microg twice daily for 2 months. Type of insulin, frequency of insulin administration, and diet were kept constant, and insulin dosage was adjusted, as needed, to maintain optimal control of glycemia. Mean body weight, daily insulin dosage, daily caloric intake, 10-hour mean blood glucose concentration, blood glycated hemoglobin concentration, and serum fructosamine concentration were not markedly different when dogs were treated with insulin and chromium picolinate, compared with insulin alone. Adverse effects were not identified with chromium picolinate administration. Results of this study suggest that, at a dosage range of 20-60 microg/kg/d, chromium picolinate caused no beneficial or harmful effects in insulin-treated diabetic dogs.     

Advanced glycation end products and sorbitol in blood from differently compensated diabetic dogs

Canine diabetes mellitus (DM) is a common metabolic disorder with long term complications, most of which are caused by glycosylation of structural proteins, decreases in antioxidant concentrations, altered osmotic balance and hypoxia due to impaired oxygen transport. Previous studies have demonstrated that under hyperglycemic conditions canine erythrocytes undergo swelling, probably due to activation of the polyol pathway. The present work aimed to assess the plasma concentration of advanced glycation end (AGE) products, stable Amadori-products generated by non-enzymatic glycosylation of proteins and the intracellular concentration of sorbitol, produced by the activation of polyol pathway in 34 blood samples from diabetic dogs and in 14 controls. AGE products were significantly higher (p<0.01) in plasma from diabetic dogs compared with control animals. The sorbitol concentration in erythrocytes was also significantly higher in diabetic dogs and, in particular, in poorly compensated animals and in dogs with ketonuria. In five cases that were analysed before and after clinical improvement, sorbitol concentration was found to correlate with improvement. These results suggest that non-specific glycosylation is increased and that the polyol pathway is activated in diabetic dogs in a manner that is proportionate to the severity of disease. Moreover, the concentration of AGE products and sorbitol may be useful for monitoring the onset of diabetic complications and assessing the most appropriate therapeutic approaches for management of canine DM.     

Effect of octreotide on plasma concentrations of glucose, insulin, glucagon, growth hormone, and cortisol in healthy dogs and dogs with insulinoma

The inhibitory effect of the somatostatin analogue octreotide on the secretion of insulin could be used in the treatment of insulinoma. However, current information on the effectiveness of octreotide in dogs is conflicting. Therefore, the endocrine effects of a single subcutaneous dose of 50 microg octreotide were studied in healthy dogs in the fasting state (n=7) and in dogs with insulinoma (n=12). Octreotide did not cause any adverse effects. In healthy dogs in the fasting state, both plasma insulin and glucagon concentrations declined significantly. Basal (non-pulse related) GH and ACTH concentrations were not affected. A slight but significant decrease in the plasma glucose concentrations occurred. Dogs with insulinoma had significantly higher baseline insulin concentrations and lower baseline glucose concentrations than healthy dogs in the fasting state. Plasma glucagon, GH, ACTH, and cortisol concentrations did not differ from those in healthy dogs. Baseline plasma insulin concentrations decreased significantly in dogs with insulinoma after octreotide administration, whereas plasma concentrations of glucagon, GH, ACTH, and cortisol did not change. In contrast to the effects in the healthy dogs, in the dogs with insulinoma plasma glucose concentrations increased. Thus, the consistent suppression of plasma insulin concentrations in dogs with insulinoma, in the absence of an suppressive effect on counter-regulatory hormones, suggests that further studies on the effectiveness of slow-release preparations in the long-term medical treatment of dogs with insulinoma are warranted.     

Outcome of dogs with diabetic ketoacidosis: 127 dogs (1993-2003)

The aim of this study was to retrospectively describe the outcome of 127 dogs with naturally occurring diabetic ketoacidosis (DKA) and to examine the association between outcome of canine DKA and clinical and clinicopathologic findings. Eighty-two (65%) dogs were diagnosed with DKA at the time of initial diagnosis of diabetes mellitus (DM). Eighty-seven dogs (69%) had one or more concurrent disorders diagnosed at the time of hospitalization. Commonly identified concurrent conditions included acute pancreatitis (52, 41%), urinary tract infection (21, 20%), and hyperadrenocorticism (19, 15%). Dogs with coexisting hyperadrenocorticism were less likely to be discharged from the hospital (P = .029). Of 121 treated dogs, 89 dogs (70%) survived to be discharged from the hospital, with a median hospitalization of 6 days. Nonsurvivors had lower ionized calcium concentration (P < .001), lower hematocrit (P = .036), lower venous pH (P = .0058), and larger base deficit (P = .0066) than did survivors. Time from admission to initiation of subcutaneous insulin therapy was correlated with lower serum potassium concentration (P = .0056), lower serum phosphorus concentration (P = .0043), abnormally high white blood cell count (P = .0060), large base deficit (P = .0015), and low venous pH (P < .001). Multivariate analysis showed that base deficit was associated with outcome (P = .021). For each unit increase in the base deficit, there was a 9%) greater likelihood of discharge from the hospital. In conclusion, the majority of dogs with DKA were not previously diagnosed with DM. Concurrent conditions and electrolyte abnormalities are common in DKA and are associated with length of hospitalization. Survival was correlated to degree of anemia, hypocalcemia, and acidosis.     

Novel diabetes mellitus treatment: mature canine insulin production by canine striated muscle through gene therapy

Muscle-targeted gene therapy using insulin genes has the potential to provide an inexpensive, low maintenance alternative or adjunctive treatment method for canine diabetes mellitus. A canine skeletal muscle cell line was established through primary culture, as well as through transdifferentiation of canine fibroblasts after infection with a myo-differentiation gene containing adenovirus vector. A novel mutant furin-cleavable canine preproinsulin gene insert (cppI4) was designed and created through de novo gene synthesis. Various cell lines, including the generated canine muscle cell line, were transfected with nonviral plasmids containing cppI4. Insulin and desmin immunostaining were used to prove insulin production by muscle cells and specific canine insulin ELISA to prove mature insulin secretion into the medium. The canine myoblast cultures proved positive on desmin immunostaining. All cells tolerated transfection with cppI4-containing plasmid, and double immunostaining for insulin and desmin proved present in the canine cells. Canine insulin ELISA assessment of medium of cppI4-transfected murine myoblasts and canine myoblast and fibroblast mixture proved presence of mature fully processed canine insulin, 24 and 48 h after transfection. The present study provides proof of principle that canine muscle cells can be induced to produce and secrete canine insulin on transfection with nonviral plasmid DNA containing a novel mutant canine preproinsulin gene that produces furin-cleavable canine preproinsulin. This technology could be developed to provide an alternative canine diabetes mellitus treatment option or to provide a constant source for background insulin, as well as C-peptide, alongside current treatment options.     

Effects of chronic obesity and weight loss on plasma ghrelin and leptin concentrations in dogs

The objective of this study was to evaluate, in dogs, the effects of obesity and weight loss on plasma total ghrelin and leptin concentrations. Twenty-four Beagle dogs, 12 control lean and 12 obese dogs of both genders and aged between 1 and 9 years, were used for the experiments. Mean body weight was 12.7+/-0.7 kg for the lean group and 21.9+/-0.8 kg for the obese group. The trial was divided into three phases. During phase 1, all 24 Beagle dogs were fed a maintenance diet. During phase 2, the obese dogs were submitted to a weight loss protocol with a high protein-low energy diet. The weight loss protocol ended once dogs reached optimal body weight. During phase 3, the dogs that were submitted to the weight loss protocol were maintained at their optimal body weight for 6 months. Plasma total ghrelin, leptin, insulin and glucose concentrations were measured to evaluate the effects of obesity and weight loss on these parameters in dogs. Body weight, body condition score, thoracic and pelvic perimeters, and ingested food amounts were also recorded during the study. Obese dogs demonstrated a significant decrease in plasma ghrelin and a significant increase in plasma leptin and insulin concentrations when compared with control dogs. During weight loss, significant increases in plasma total ghrelin and glucose and significant decreases in plasma leptin and insulin were observed. The increase in plasma ghrelin concentrations seemed to be transient. Body weight and the morphometric parameters correlated positively with leptin concentrations and negatively with total ghrelin concentrations. These results suggest that ghrelin and leptin could play a role in dogs in the adaptation to a positive or negative energy balance, as observed in humans.     

Effects of pentobarbitone anaesthesia and atropine on the intravenous glucose tolerance test in normal dogs

The effect of atropine (0·1 mg/kg b.w. s.c.) and of pentobarbitone anaesthesia (25 mg/kg b.w.) on the plasma glucose clearance and insulin response to an intravenous load of 600 mg and 1,250 mg/kg b.w. glucose was studied in twenty-four normal young Dalmatian dogs (ten male, fourteen female). Neither the rate of disappearance of glucose from the circulation, nor the insulin release following both glucose loads was altered by atropine. However, the disposal of intravenous glucose was significantly (P < 0·01) delayed and the insulin release significantly decreased under pentobarbitone anaesthesia. It is suggested that a decreased blood flow through the pancreas during pentobarbitone anaesthesia is most likely the cause of the decreased insulin release which in turn causes a delayed rate of disappearance of glucose from the circulation. It is therefore concluded that an intravenous glucose tolerance test, as diagnostic procedure, should never be done in anaesthetized dogs.     

Anti-insulin antibodies in diabetic dogs before and after treatment with different insulin preparations

Background: Anti‐insulin antibodies (AIA) occur in diabetic dogs after insulin therapy, although their clinical significance is unclear. Hypothesis: Treatment of diabetic dogs with heterologous insulin is more likely to stimulate production of AIA than is treatment with homologous insulin. Animals: Diabetic dogs sampled before insulin therapy (n = 40), diabetic dogs sampled following treatment with porcine (homologous) insulin (n = 100), bovine (heterologous) lente insulin (n = 100), or bovine protamine zinc (PZI) insulin (n = 20), and nondiabetic control dogs (n = 120). Methods: Prospective observational study. Sera were analyzed by ELISA for antibodies against porcine insulin, bovine insulin, insulin A, B, or C peptides, and control antigens; canine distemper virus (CDV) and canine thyroglobulin (TG). Canine isotype‐specific antibodies were used to determine total and anti‐insulin IgG1 : IgG2 ratios. Results: There was no difference in CDV or TG reactivity among the groups. AIA were detected in 5 of 40 newly diagnosed (untreated) diabetic dogs. There was no significant difference in AIA (ELISA optical density reactivity) comparing control and porcine insulin‐treated diabetic dogs (P > .05). Anti‐insulin reactivity was most prevalent in bovine PZI insulin‐treated dogs (90%; P < .01), and bovine lente insulin‐treated dogs (56%; P < .01). AIA induced by treatment were enriched for the IgG1 isotype. Conclusions and Clinical Importance: This study indicates that bovine insulin is more immunogenic than porcine insulin when used for treatment of diabetic dogs.     

Oxyntomodulin increases the concentrations of insulin and glucose in plasma but does not affect ghrelin secretion in Holstein cattle under normal physiological conditions

Ghrelin, the natural ligand of the growth hormone secretagogue receptor (GHS-R1a), has been shown to stimulate growth hormone (GH) secretion. Regulation of ghrelin secretion in ruminants is not well studied. We investigated the effects of oxyntomodulin (OXM) and secretin on the secretions of ghrelin, insulin, glucagon, glucose, and nonesterified fatty acids (NEFA) in pre-ruminants (5 wk old) and ruminants (10 wk old) under normal physiological (feeding) conditions. Eight male Holstein calves (pre-ruminants: 52 ± 1 kg body weight [BW]; and ruminants: 85 ± 1 kg BW) were injected intravenously with 30 μg of OXM/kg BW, 50 μg of secretin/kg BW, and vehicle (0.1% bovine serum albumin [BSA] in saline as a control) in random order. Blood samples were collected, and plasma hormones and metabolites were analyzed using a double-antibody radioimmunoassay system and commercially available kits, respectively. We found that OXM increased the concentrations of insulin and glucose but did not affect the concentrations of ghrelin in both pre-ruminants and ruminants and that there was no effect of secretin on the concentrations of ghrelin, insulin, and glucose in these calves. We also investigated the dose-response effects of OXM on the secretion of insulin and glucose in 8 Holstein steers (401 ± 1 d old, 398 ± 10 kg BW). We found that OXM increased the concentrations of insulin and glucose even at physiological plasma concentrations, with a minimum effective dose of 0.4 μg/kg for the promotion of glucose secretion and 2 μg/kg for the stimulation of insulin secretion. These findings suggest that OXM takes part in glucose metabolism in ruminants.     

Serum and skin IgA concentrations in normal and atopic dogs

Objective To compare serum and skin surface IgA concentrations from atopic and normal dogs.
Procedure IgA concentrations in sera and skin washings of 20 clinically normal dogs that had no history of pruritus or skin disease were compared to those obtained in 20 dogs with a diagnosis of atopy determined by history, clinical examination and positive intradermal skin test.
Results There was no significant difference in the mean serum IgA concentration in normal dogs (252 ± 187 mg/L) versus atopic animals (314 ± 327). When skin washings from all sites in both groups were compared, atopic dogs had significantly greater concentrations of IgA in their skin washings than normal dogs as evaluated by an enzyme-linked immunoassay (P < 0.001). However, there was no significant difference between the individual sites of the skin washings of atopic and normal dogs.
Conclusion IgA concentrations of skin washings in atopic dogs were greater than in normal dogs. Further investigations need to determine if the greater concentrations were caused by nonspecific inflammation or by secretion of allergen-specific IgA onto the skin surface.     

Effects of feeding pattern on ghrelin and insulin secretion in pigs

Ghrelin is a peptide hormone that has been implicated in the regulation of feed intake, but little is known about its secretion in pigs. Hence, the effect of feeding pattern on the regulation of ghrelin secretion was tested. In experiment 1, barrows were allotted randomly into 1 of 2 groups, (1) ad libitum fed (CONT) and (2) limited access to feed (once per day, MEAL). Blood samples were taken through jugular catheters every 15 min for 6 h after 7 d on the experimental feeding regimen. Plasma concentrations of ghrelin and insulin were determined by radioimmunoassay. Ghrelin concentrations in the MEAL pigs were elevated before feeding and declined after feeding (P < 0.01). No pattern in plasma ghrelin concentrations was observed in the CONT pigs, but ghrelin concentrations were lower than in the MEAL group. Insulin concentrations were greater in CONT pigs (P < 0.01) during most of the sampling and increased after feeding in the MEAL pigs (P < 0.01). In experiment 2, the treatments were the same as in experiment 1; however, the amount of feed was increased in the MEAL group so that their daily intake was similar to the CONT pigs. Ghrelin concentrations in the MEAL group were again elevated before the meal and declined afterward (P < 0.01). Insulin but not glucose concentrations were negatively correlated with ghrelin. Once-per-day feeding resulted in increased plasma concentrations of ghrelin, which decreased after feeding. Ghrelin may be involved in the regulation of feed intake in pigs.     

Comparison of two insulin protocols for diabetic dogs undergoing cataract surgery

Objective To evaluate the effectiveness of two insulin doses to maintain an acceptable range of blood glucose concentrations (70–200 mg dL^?1) in the peri‐operative period in diabetic dogs. Animals Twenty‐four diabetic dogs with a median weight of 20.6 kg and a median age of 8 years old. Methods The dogs were randomly assigned to receive either 25 or 100% of their normal insulin dose subcutaneously on the morning of surgery. The anesthetic and feeding protocols were standardized. On the day before surgery, venous blood was collected for measurement of β‐hydroxybutyrate, cholesterol, glucose, glycosylated hemoglobin, hematocrit, total plasma protein and urea nitrogen. On the day of surgery, blood glucose concentrations were measured prior to anesthesia, prior to the start of surgery, 1 and 2 hours after beginning of surgery, 1 hour after extubation, at 16 : 00 hours and at 20 : 00 hours. β‐hydroxybutyrate concentrations were measured at 20 : 00 hours that day. At 08 : 00 hours the following day, β‐hydroxybutyrate and glucose concentrations were measured. The significance of differences between groups was tested with Wilcoxon's two‐tailed rank‐sum test, Chi‐square test and Fisher's exact test. Results There were no differences in insulin treatments, clinical signs, concurrent diseases and most clinicopathological parameters between the two groups of dogs at entry to the study. The 25% dose group had blood glucose values of 296 (102–601) mg dL^?1 at 16 : 00 hours and 429 (97–595) mg dL^?1 at 20 : 00 hours on the day of surgery. The 100% insulin dose group had lower corresponding values of 130 (55–375) mg dL^?1 (p = 0.04) and 185 (51–440) mg dL^?1 (p = 0.004). No other differences (p < 0.05) were detected between the two groups. Conclusions The administration of a full dose of insulin is only marginally advantageous for reducing glucose to normal (70–120 mg dL^?1) after anesthesia but neither dose consistently induced glycemic values in an acceptable range (70–200 mg dL^?1) or normoketonemia. Clinical relevance Blood glucose should be measured immediately before anesthesia and periodically throughout the peri‐operative period in all diabetic dogs because presurgical subcutaneous administration of 25 or 100% of the normal insulin dose resulted in unpredictable blood glucose concentrations.     

Plasma leptin concentration in dogs: effects of body condition score, age, gender and breeds

Leptin is a cytokine produced by adipocytes, and plays a key role in the regulation of energy balance. In the present study, we measured plasma leptin concentrations of 166 normal and obese dogs visiting veterinary practices, and clarified the influence of age, gender and breed on plasma leptin levels in dogs. Leptin levels were higher in the dogs with higher body condition scores. There was no noticeable influence of age, gender and breed, but those in optimal puppies and obese Miniature Dachshund tended to be lower than those in corresponding groups. We conclude that plasma leptin is a reliable marker of adiposity in dogs regardless of age, gender and breed variations, and thereby useful as a blood biochemistry test for health examinations and treatment of obesity.     

Absorption kinetics of regular and isophane (NPH) insulin in the normal dog

Absorption kinetics of regular and isophane (NPH) insulins were evaluated in seven normal fasted dogs by measuring serial serum concentrations of insulin and glucose following the subcutaneous administration of regular and NPH insulins. These results were compared to serum insulin values determined after injecting similar doses of regular insulin intravenously. Regular insulin was better absorbed than NPH insulin (mean bioavailability index 64.6% vs. 41.1%, P less than .01) resulting in a significantly greater maximal increase in mean circulating insulin concentrations above baseline values (362.2 microU/ml vs. 147.8 microU/ml, P less than .05). The time interval between insulin injection and return of serum insulin values to basal concentrations was also significantly shorter for regular than for NPH insulin (4.9 hr vs. 8.6 hr, P less than .05). However, there were no significant differences between regular and NPH insulins in time to reach peak serum insulin concentrations, maximal reduction in serum glucose concentrations, or time of lowest circulating glucose levels. The results of this study support previously accepted values for time-action characteristics of regular insulin, but suggest that NPH insulin may have an earlier peak and shorter duration of action than has previously been proposed in the dog.     

Changes of cardiac function in diabetic dogs

Objective

This study aimed to evaluate cardiac function and compare the concentration of cardiac biomarkers including cardiac troponin I (cTnI), galectin-3 (Gal-3), and N-terminal pro B-type natriuretic peptides (NT-proBNP) in diabetic and control dogs.