Distribution of K and L cells in the feline intestinal tract.

Glucose-dependent insulinotropic peptide (GIP), glucagon-like peptide (GLP)-1 and GLP-2 are hormones secreted from specialized K cells (GIP) and L cells (GLP-1, GLP-2) in the intestinal mucosa. These hormones play major roles in health and disease by modulating insulin secretion, satiety, and multiple intestinal functions. The aim of this study was to describe the distribution of K cells and L cells in the intestines of healthy cats. Samples of duodenum, mid-jejunum, ileum, cecum, and colon were collected from 5 cats that were euthanized for reasons unrelated to this study and had no gross or histologic evidence of gastrointestinal disease. Samples stained with rabbit-anti-porcine GIP, mouse-anti-(all mammals) GLP-1, or rabbit-anti-(all mammals) GLP-2 antibodies were used to determine the number of cells in 15 randomly selected 400× microscopic fields. In contrast to other mammals (eg, dogs) in which K cells are not present in the ileum and aborally, GIP-expressing cells are abundant throughout the intestines in cats (>6/high-power field in the ileum). Cells expressing GLP-1 or GLP-2 were most abundant in the ileum (>9/high-power field) as in other mammals, but, although GLP-1-expressing cells were abundant throughout the intestines, GLP-2-expressing cells were rarely found in the duodenum. In conclusion, the distribution of GIP-secreting K cells in cats is different from the distribution of K cells that is described in other mammals. The difference in distribution of GLP-2- and GLP-1-expressing cells suggests that more than 1 distinct population of L cells is present in cats.

Skeletal muscle tissue transcriptome differences in lean and obese female beagle dogs.

Skeletal muscle is a large and insulin-sensitive tissue that is an important contributor to metabolic homeostasis and energy expenditure. Many metabolic processes are altered with obesity, but the contribution of muscle tissue in this regard is unclear. A limited number of studies have compared skeletal muscle gene expression of lean and obese dogs. Using microarray technology, our objective was to identify genes and functional classes differentially expressed in skeletal muscle of obese (14.6 kg; 8.2 body condition score; 44.5% body fat) vs. lean (8.6 kg; 4.1 body condition score; 22.9% body fat) female beagle adult dogs. Alterations in 77 transcripts was observed in genes pertaining to the functional classes of signaling, transport, protein catabolism and proteolysis, protein modification, development, transcription and apoptosis, cell cycle and differentiation. Genes differentially expressed in obese vs. lean dog skeletal muscle indicate oxidative stress and altered skeletal muscle cell differentiation. Many genes traditionally associated with lipid, protein and carbohydrate metabolism were not altered in obese vs. lean dogs, but genes pertaining to endocannabinoid metabolism, insulin signaling, type II diabetes mellitus and carnitine transport were differentially expressed. The relatively small response of skeletal muscle could indicate that changes are occurring at a post-transcriptional level, that other tissues (e.g., adipose tissue) were buffering skeletal muscle from metabolic dysfunction or that obesity-induced changes in skeletal muscle require a longer period of time and that the length of our study was not sufficient to detect them. Although only a limited number of differentially expressed genes were detected, these results highlight genes and functional classes that may be important in determining the etiology of obesity-induced derangement of skeletal muscle function.

The GLP-1 mimetic exenatide potentiates insulin secretion in healthy cats.

The glucagon-like peptide-1 mimetic exenatide has a glucose-dependent insulinotropic effect, and it is effective in controlling blood glucose (BG) with minimal side effects in people with type 2 diabetes. Exenatide also delays gastric emptying, increases satiety, and improves ß-cell function. We studied the effect of exenatide on insulin secretion during euglycemia and hyperglycemia in cats. Nine young, healthy, neutered, purpose-bred cats were used in a randomized, cross-over design. BG concentrations during an oral glucose tolerance test were determined in these cats previously. Two isoglycemic glucose clamps (mimicking the BG concentration during the oral glucose tolerance test) were performed in each cat on separate days, one without prior treatment (IGC) and the second with exenatide (1 µg/kg) injected subcutaneously 2 h before (ExIGC). BG, insulin, and exenatide concentrations were measured, and glucose infusion rates were recorded and compared in paired tests between the two experiments. After exenatide injection, insulin serum concentrations increased significantly (2.4-fold; range 1.0- to 9.2-fold; P = 0.004) within 15 min. This was followed by a mild decrease in BG concentration and a return of insulin concentration to baseline despite a continuous increase in serum exenatide concentrations. Insulin area under the curve (AUC) during ExIGC was significantly higher than insulin AUC during IGC (AUC ratio, 2.0 ± 0.4; P = 0.03). Total glucose infused was not significantly different between IGC and ExIGC. Exenatide was detectable in plasma at 15 min after injection. The mean exenatide concentration peaked at 45 min and then returned to baseline by 75 min. Exenatide was still detectable in the serum of three of five cats 8 h after injection. No adverse reactions to exenatide were observed. In conclusion, exenatide affects insulin secretion in cats in a glucose-dependent manner, similar to its effect in other species. Although this effect was not accompanied by a greater ability to dispose of an intravenous glucose infusion, other potentially beneficial effects of exenatide on pancreatic ß cells, mainly increasing their proliferation and survival, should be investigated in cats.

The incretin effect in cats: comparison between oral glucose, lipids, and amino acids.

Incretin hormones are secreted from the intestines in response to specific nutrients. They potentiate insulin secretion and have other beneficial effects in glucose homeostasis. We aimed to study the incretin effect in cats and to compare the effect of oral glucose, lipids, or amino acids on serum concentrations of insulin, total glucose-dependent insulinotropic peptide (GIP) and total glucagon-like peptide 1 (GLP-1). Ten healthy cats were used in a repeated measures design. Glucose, lipid, or amino acids were administered through nasoesophageal tubes on separate days. Blood glucose (BG) concentrations were matched between experiments by measuring BG every 5 min and infusing glucose intravenously at a changing rate. Intravenous glucose infusion with no prior treatment served as control. The incretin effect was estimated as the difference in insulin area under the curve (AUC) after oral compared with intravenous glucose. Temporal changes and total amount of hormone secretions were compared between treatment groups with the use of mixed models. Total glucose infused (TGI) at a mean dose of 0.49 g/kg resulted in slightly higher BG compared with 1 g/kg oral glucose (P = 0.038), but insulin concentrations were not significantly different (P = 0.367). BG and the TGI were not significantly different after the 3 oral challenges. Total GIP AUC was larger after lipids compared with amino acids (P = 0.0012) but GIP concentrations did not increase after oral glucose. Insulin and GIP concentrations were positively correlated after lipid (P < 0.001) and amino acids (P < 0.001) stimulations, respectively, but not after oral glucose stimulation. Total GLP-1 AUC was similar after all three oral stimulations. Insulin and GLP-1 concentrations were positively correlated after glucose (P = 0.001), amino acids (P < 0.001), or lipids (P = 0.001) stimulations. Our data indirectly support an insulinotropic effect of GIP and GLP-1. Potentiation of insulin secretion after oral glucose is minimal in cats and is mediated by GLP-1 but not GIP.

Dietary macronutrients and feeding frequency affect fasting and postprandial concentrations of hormones involved in appetite regulation in adult dogs.

Identifying dietary effects on appetite-regulating hormones will enhance our understanding of appetite control. Before complex diets are tested, effects of specific macronutrients or feeding frequency should be identified. The objectives of this nutrition study were to identify differences in endocrine response with feeding frequency (Exp. 1) and after a single dose of a sole macronutrient (Exp. 2). A control diet supplying similar energy content from carbohydrate, protein, and fat was fed to maintain ideal BW. In Exp. 1, 8 healthy adult (1.9 ± 0.1 yr old) female hound cross dogs with an average BW of 22 kg (4.8 ± 0.8 BCS based on a 9-point scale) were randomly allotted to 1 of 2 treatments (fed once or twice daily) in a crossover design. After a 14-d adaptation period, a blood sample was taken (10 mL) before feeding, and samples were collected every 2 h postprandially for 24 h. In Exp. 2, dogs were randomly allotted to 1 of 4 treatments in a 4 × 4 Latin square design. After a 6-d adaptation period, the normal meal on d 7 was replaced with a bolus of maltodextrin (50 g in water; CARB), canned chicken (50 g; PROT), lard (25 g; fat), or water (200 mL). A blood sample (10 mL) was taken at 0, 30, 60, 90, 120, 150, 180, 240, 300, and 360 min postprandial. Total ghrelin, active glucagon-like peptide-1 (GLP-1), insulin, and glucose concentrations were measured. Data were analyzed to compare changes from baseline and area under the curve (AUC) among treatments. In Exp. 1, all hormones were quite variable throughout the day, with a few insulin and GLP-1 differences because of feeding frequency. In Exp. 2, CARB produced a marked peak in glucose and insulin concentrations compared with PROT, fat, or water, resulting in increased glucose (P < 0.001) and insulin (P = 0.07) incremental AUC values. On the other hand, the fat treatment led to increased GLP-1 concentrations over time. Ghrelin AUC was not different among treatments. The circulating hormone data were highly variable and indicate that diet plays a role in insulin and GLP-1 secretion, but more research is required to elucidate these effects.

Pharmacodynamics of insulin detemir and insulin glargine assessed by an isoglycemic clamp method in healthy cats.

BACKGROUND: Insulin detemir and insulin glargine are synthetic long-acting insulin analogs. In people, insulin glargine is longer acting and has a relatively flat time-action profile, while insulin detemir has significantly less within-subject variability. Insulin detemir is also associated with less undesired weight gain and decreased frequency of hypoglycemic events. OBJECTIVES: To compare the pharmacodynamics of insulin detemir and insulin glargine in healthy cats. ANIMALS: Ten young, healthy, neutered, purpose-bred cats. METHODS: Randomized, cross-over design. Pharmacodynamics of insulin detemir and insulin glargine were determined by the isoglycemic clamp method after a 0.5 U/kg SC injection. RESULTS: The only significant difference in the pharmacodynamics of insulin detemir and insulin glargine was onset of action (1.8+/-0.8 and 1.3+/-0.5 hours for insulin detemir and insulin glargine, respectively, P=.03). End of action of insulin detemir was reached at 13.5+/-3.5 hours and for insulin glargine at 11.3+/-4.5 hours (P=.18). Time-to-peak action of insulin detemir was reached at 6.9+/-3.1 hours and for insulin glargine at 5.3+/-3.8 hours (P=.7). The time-action curves of both insulin analogs varied between relatively flat curves in some cats and peaked curves in others. CONCLUSION AND CLINICAL IMPORTANCE: Insulin detemir and insulin glargine have shorter durations of action than in people when assessed by the clamp method, but in some cats these insulin analogs could be useful as once-a-day drugs. Peak effects of both insulin analogs are pronounced in some cats.

Cloning and sequencing of the calcium-sensing receptor from the feline parathyroid gland.

Messenger RNA of the calcium-sensing receptor from feline parathyroid gland (fCaSR) was reversed transcribed to cDNA, amplified by polymerase chain reaction (PCR) and cloned into E. coli. Sequences obtained from cloned E. coli were used for genetic characterization of the fCaSR mRNA and for exonic PCR primer design. Multiple fCaSR exons sequence alignments obtained from PCR amplification of genomic DNA of 5 healthy domestic shorthair cats indicated the presence of 3 synonymous missense single-nucleotide polymorphisms (SNP) and 1 nonsynonymous missense SNP, which changed an amino acid from arginine to proline. The fCaSR has 96%, 96%, and 94% homology to the canine, human, and bovine amino acid sequences, respectively.