Dietary choline, but not L-carnitine, increases circulating lipid and lipoprotein concentrations, without affecting body composition, energy expenditure or respiratory quotient in lean and obese male cats during weight maintenance.

INTRODUCTION

Due to the involvement in one-carbon metabolism and lipid mobilization, choline and L-carnitine supplementation have been recommended to minimize hepatic lipid accumulation and support fat oxidation, respectively. This study investigated the lipotropic benefits of choline or L-carnitine supplementation in lean and obese cats maintaining body weight (BW).

METHODS

Lean [ = 9; body condition score (BCS): 4-5/9] and obese ( = 9; BCS: 8-9/9) adult male neutered colony cats were used in a replicated 3 x 3 complete Latin square design. Treatments included choline (378 mg/kg BW), L-carnitine (200 mg/kg BW) and control (no supplement). Treatments were supplemented to the food for 6 weeks each, with a 2-week washout between treatments. Cats were fed once daily to maintenance energy requirements, and BW and BCS were assessed weekly. Fasted blood collection, indirect calorimetry, and dual-energy X-ray absorptiometry occurred at the end of each treatment period. Serum was analyzed for cholesterol (CHOL), high-density lipoprotein CHOL (HDL-C), triglycerides (TAG), non-esterified fatty acids (NEFA), glucose, creatinine (CREAT), urea, alkaline phosphatase (ALP) and alanine aminotransferase (ALT). Very low-density lipoprotein CHOL (VLDL) and low-density lipoprotein CHOL (LDL-C) were calculated. Data were analyzed using proc GLIMMIX, with group and period as random effects, and treatment, body condition, and their interaction as fixed effects, followed by a Tukey's test when significance occurred.

RESULTS

Cats supplemented choline had lower food intake ( = 0.025). Treatment did not change BW, BCS and body composition ( > 0.05). Obese cats had greater ALP, TAG, and VLDL, and lower HDL-C compared to lean cats ( < 0.05). Choline resulted in greater CHOL, HDL-C, LDL-C and ALT ( < 0.05). L-carnitine resulted in lower CREAT ( = 0.010). Following the test, differences between treatment means were not present for ALP ( = 0.042). No differences were found for glucose, urea or NEFA ( > 0.05). Obese cats had a lower fed respiratory quotient (RQ), regardless of treatment ( = 0.045). Treatment did not affect fed or fasted RQ and energy expenditure ( > 0.05).

DISCUSSION

Choline appeared to increase circulating lipid and lipoprotein concentrations regardless of body condition, likely through enhanced lipid mobilization and hepatic elimination. Neither dietary choline or L-carnitine altered body composition or energy metabolism in the lean or obese cats, as compared to control.