Obesity is a health concern for domestic cats. Obesity and severe energy restriction predispose cats to feline hepatic lipidosis. As choline is linked to lipid metabolism, we hypothesized that dietary choline supplementation would assist in reducing hepatic fat through increased lipoprotein transport and fatty acid oxidation. Twelve obese cats (body condition score [BCS] ≥ 8/9) were split into two groups. Cats were fed a control (n = 6; 4587 mg choline/kg dry matter [DM]) or a high choline diet (n = 6; 18,957 mg choline/kg DM) for 5 weeks, for adult maintenance. On days 0 and 35, fasted blood was collected, and the body composition was assessed. Serum lipoprotein and biochemistry profiles, plasma amino acids and plasma acylcarnitines were analyzed. The body weight, BCS and body composition were unaffected (p > 0.05). Choline increased the serum cholesterol, triacylglycerides, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, very low-density lipoprotein cholesterol and plasma methionine (p < 0.05) and decreased the serum blood urea nitrogen and alkaline phosphatase (p < 0.05). Choline also reduced the plasma acylcarnitine to free carnitine ratio (p = 0.006). Choline may assist in eliminating hepatic fat through increased fat mobilization and enhanced methionine recycling.

Gonadectomy is a major risk factor for feline obesity. The lipotropic effects of choline have demonstrated benefits for growth and carcass composition in livestock. The consumption of supplemental choline on body weight (BW), body composition, lipid metabolism, energy expenditure (EE), and serum satiety hormones were evaluated in 15 gonadectomized male kittens. Kittens were offered a base diet formulated for growth (3310mg choline/kg dry matter [DM]) to daily energy requirements (DER) over an 11-week acclimation. Post-gonadectomy, kittens were assigned to a base diet (CONTROL, n = 7) or choline group (base diet with additional choline at 300mg/kg BW0.75 as a top dress) (CHOLINE, n = 8). For 12-weeks post-neuter, kittens were offered three times their DER over three meals to mimic ad libitum feeding. At week -1 and 12, body composition was assessed using dual energy x-ray absorptiometry (DXA), 24-hour indirect calorimetry was performed for EE and respiratory quotients (RQ), and fasted serum samples were analyzed for lipid compounds and satiety hormones. Daily food intake (FI) and weekly BW were measured. Data was analyzed as a repeated measures of variance (ANCOVA) using the GLIMMIX procedure with time and group as fixed effects. CHOLINE had lower mean daily FI and lower rates of BW accretion (P<0.05) in contrast to CONTROL. All absolute body composition data increased over time for both groups, with lower increases in total tissue mass (P = 0.031) and fat mass (P = 0.005) in CHOLINE. Serum satiety hormones and lipid compounds did not differ (P>0.05) between groups, but both groups experienced a decrease in low-density lipoproteins and increase in high-density lipoproteins (P<0.05). Primary substrate utilization showed lipid use when fasted and use of protein or mixed macronutrients in the fed state. Fed state EE decreased post-gonadectomy (P = 0.004), however, CHOLINE did not affect total EE or RQ. These results suggest that supplemental dietary choline reduces FI, BW, and fat mass and may help to reduce the propensity of weight gain and subsequent obesity in gonadectomized feline populations.

This study adapted the established glycemic index (GI) methodology used in human research to perform two studies in sled dogs in order to assess the blood glucose raising potential of pulse-based dog foods. The first was a pilot study (n=6 dogs) to determine the GI of single starch sources (white bread, cooked white rice and cooked green lentils) using a glucose solution as control. Next, the effect on glycemic and insulinemic meal responses and GI of commercial extruded dog foods containing different categories of starch sources (traditional grain, whole grain, grain-free and vegan) were investigated on n=11 dogs using a glucose control. Results were compared using repeated measures ANOVA. Consumption of 10 g of available carbohydrate (Av CHO) was insufficient to elicit a measurable response in blood glucose for GI determination, and as such, the amount was increased to 25 g for the second study. The glycemic index (±SE) of the single starch sources and dog foods were: white bread 47 ± 11; cooked white rice 71 ± 14; cooked green lentils 60 ± 20 (p = 0.569); traditional grain 83 ± 17; whole grain 56 ± 8; grain-free 41± 6; and vegan 65 ± 15 (p = 0.154) . No statistical differences in glycemic response over time were observed between the single starch sources or the extruded diets tested (p =0.1412; p =0.2651). Insulinemic response elicited by the extruded diets was also not different (p = 0.079); however the traditional grain diet did have the slowest time to peak for insulin (p = 0.0078). Among single starch sources and extruded dog foods, there were no differences in the glycemic indices measured in this study. The GI methodology has not been validated for use in canine species and it is likely that our results were due to higher inter-individual variation or inadequate study power. Regardless, this study will serve to better define future studies to investigate the potential physiological benefits of low glycemic index foods for dogs.

Choline is an essential nutrient linked to hepatic lipid metabolism in many animal species, including cats. The current study investigated the serum lipid profiles, serum liver enzymes, respiratory quotients and energy expenditures of overweight cats fed maintenance diets, in response to graded doses of supplemental dietary choline. Overweight (body condition score [BCS]:≥6/9) adult male neutered cats (n=14) were supplemented with five choline chloride doses for three-week periods, in a 5 x 5 Latin square design. Doses were based on individual body weight (BW) and the daily recommended allowance (RA) for choline (63mg/kg BW 0.67) according to the National Research Council. Doses were: control (no additional choline: 1.2 x RA, 77 mg/kg BW 0.67), 2 x RA (126mg/kg BW 0.67), 4 x RA (252mg/kg BW 0.67), 6 x RA (378mg/kg BW 0.67), and 8 x RA (504mg/kg BW 0.67). Choline was top-dressed over the commercial extruded cat food (3620mg choline/kg diet), fed once a day at maintenance energy requirements (130kcal/kgBW 0.4). Body weight and BCS were assessed weekly. Fasted blood samples were taken and indirect calorimetry was performed at the end of each three-week period. Serum was analyzed for cholesterol, high-density lipoprotein cholesterol (HDL-C), triglycerides, non-esterified fatty acids, glucose, creatinine, blood urea nitrogen (BUN), alkaline phosphatase (ALP) and alanine aminotransferase. Very low-density lipoprotein cholesterol (VLDL) and low-density lipoprotein cholesterol were calculated. Data was analyzed via SAS using proc GLIMMIX, with group and period as the random effects, and treatment as the fixed effect. Statistical significance was considered at P &lt; 0.05. Body weight and BCS did not change (P &gt; 0.05). Serum cholesterol, HDL-C, triglycerides, and VLDL increased with 6 x RA (P &lt; 0.05). Serum ALP decreased with 8 x RA (P = 0.004). Choline at 4 x and 6 x RA decreased serum BUN (P = 0.006). Fed or fasted respiratory quotient and energy expenditure did not differ among dietary choline doses (P &gt; 0.05). These results suggest that dietary choline supplementation at 6 x RA may increase hepatic fat mobilization through increased lipoprotein transport, and beneficially support hepatic health in overweight cats. Future studies that combine these results with existing knowledge of feline weight loss and hepatic lipidosis are warranted.

The objective of this study was to determine the dose-response relationship between dietary choline intake and one-carbon cycle activity in overweight cats at maintenance energy requirements. This study was approved by the University of Guelph Animal Care Committee (AUP#4118). Overweight (body condition score:≥6/9) adult male neutered cats (n = 14) received each of five choline chloride doses individually for three weeks in a 5x5 latin square design. Doses were based on body weight (BW) and the daily recommended allowance (RA) for choline for adult cats (63 mg/kg BW0.67). Doses were: 2xRA (126 mg/kg BW0.67), 4xRA (252 mg/kg BW0.67), 6xRA (378 mg/kg BW0.67), 8xRA (504 mg/kg BW0.67), and control (no additional choline). Choline was administered onto the commercial extruded cat food (3620 mg choline/kg diet), given once a day at maintenance energy requirements (130 kcal/kg BW0.4). Fasted serum samples were analyzed for metabolomics through quantitative nuclear magnetic resonance (NMR) spectroscopy and direct infusion mass spectrometry (DI-MS) at the end of each period. Data was analyzed using proc GLIMMIX in SAS, with group and period as the random effects, and dose as the fixed effect. Statistical significance was considered at P &lt; 0.05. Tukey’s post-hoc test was performed to assess multiple comparisons. Choline at 6x and 8x RA appears to increase transmethylation through the one-carbon cycle, as suggested by increased serum betaine, dimethylglycine (DMG) and methionine (P &lt; 0.05). Carnitine, methylated by s-adenosylmethionine (SAM), increased (P &lt; 0.05). Serine and threonine, precursors for the biosynthesis of homocysteine, appear to have been spared (P &lt; 0.05). Supplemental dietary choline (6x and 8xRA) may be beneficial for overweight cats, as it may increase activity of the one-carbon cycle and methyl status; which are necessary for hepatic function. To better understand the impact of choline on methylation reactions, the quantification of specific proteins, gene expression and/or conversion rates is required.