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Effects of L-Carnitine Supplement on Serum Levels of Estrogen, Progesterone and Testosterone in Felines Following Ovariohysterectomy


1 Department of Clinical Sciences, Faculty of Veterinary Medicine, Garmsar Branch, Islamic Azad University, Garmsar, IR Iran
*Corresponding Author: Azin Tavakoli, Department of Clinical Sciences, Faculty of Veterinary Medicine, Garmsar Branch, Islamic Azad University, P. O. Box: 3581631167, Garmsar, IR Iran. Tel: +98-9127693797, Fax: +98-2334552121, E-mail: azin.tavakoli@gamil.com.
Iranian Red Crescent Medical Journal. 19(1): e25666 , DOI: 10.5812/ircmj.25666
Article Type: Research Article; Received: Nov 28, 2014; Revised: May 23, 2015; Accepted: Jun 15, 2015; epub: Aug 17, 2016; collection: Jan 2017

Abstract


Background: The benefits of the addition of L-carnitine to the diet of cats to control weight gain after the removal of their ovaries have been highlighted recently. It is also used in women after menopause. Whether its supplementation alters the sexual hormones is a concern.

Objectives: The objective of this study was to evaluate the effect of dietary supplementation of L-carnitine on estrogen, progesterone and testosterone in cats following ovariohysterectomy.

Methods: Conventional midline ovariohysterectomy was performed in 14 DSH adult and healthy female cats. 10 days after the surgery, the cats were divided into two groups randomly. In group 2, a single dose of 100 mg/kg/day L-carnitine was added to the regular diet for 50 days. The cats in group 1 received no L-carnitine in their diet. Blood samples were taken from all cats prior to surgery, and then again 10 and 60 days post-operatively. Serum levels of estrogen, progesterone and testosterone were measured using a commercially available AMH enzyme-linked immunosorbent assay (ELISA).

Results: Serum levels of estrogen and progesterone significantly decreased at 10 days after the surgery in all cats (P < 0.05). There was no significant difference in serum level of testosterone prior and after the surgery between the groups. Also, no significant difference was observed in serum levels of estrogen, progesterone and testosterone at 60 days after the surgery between the groups (P > 0.05).

Conclusions: It is concluded that dietary supplementation of L-carnitine has no effect on serum levels of estrogen, progesterone and testosterone in cats following ovariohysterectomy. Long-term study is recommended.

Keywords: L-Carnitine; Sexual Hormone; Ovariohysterectomy; Feline

1. Background


The benefits of the addition of L-carnitine to the canine and feline diet to control weight gain have been highlighted recently. L-carnitine is a vitamin-like compound made in the body from the amino acids lysine and methionine. It is an important nutrient that acts as a transport for fatty acids into the mitochondria of cells and is essential for the cellular production of energy (1). It promotes cardiovascular health and prevents increases in body weight. Recent scientific works indicate that it helps reduce weight in overweight dogs and cats (2, 3). Dietary supplementation of L-carnitine to obese cats’ diet was shown to affect the metabolic rate and cause rapid weight loss (4). Ovariohysterectomy is one of the most common surgical procedures performed in small animal practice (5). It is the method of choice for sterilization in dogs and cats (6, 7). Although ovariohysterectomy helps to effectively control overpopulation, it is a risk factor for feline obesity (8). It has been shown that the changes in feeding behavior and increase in calorie intake after ovariohysterectomy are responsible for changes in body composition and weight gain in cats (9, 10). In addition, it has been proved that energy requirements are 20% lower after the removal of the ovaries (11). Therefore, we would expect weight gain in cats after spaying. Veterinarians have worked to prevent weight gain in cats following ovariohysterectomy. Exercise, restriction in dietary intake, special post-operative diets and dietary supplements are recommended for the prevention of obesity in spayed cats (9, 12). Among food supplements, L-carnitine is very frequently prescribed for cats to manage weight gain after sterilization.


All steroid hormones are synthesized from cholesterol. The ovaries and adrenal cortex are traditionally responsible for most of the production of steroids in female cats. However, it is shown that adipose tissue significantly contributes to the production of estrogen (13). This means fatter animals could be expected to have higher levels of estrogen, especially after gonadectomy (14). In addition, L-carnitine is typically considered to be a fat burner and has been used for fat metabolism in other species (5, 6). It may affect levels of sexual hormones following ovariohysterectomy by affecting fat cells and cholesterol, which are basic components of steroid hormones. Limited studies have been conducted to evaluate the effects of L-carnitine on sexual hormones like testosterone and prolactin in humans, especially in males. It is reported that carnitine deficiency is independently associated with low free testosterone levels in male hemodialysis patients. Also, testosterone and carnitines proved to be effective in the treatment of male aging syndrome (14, 15). L-carnitine leads to significant weight loss and is recommended in women following menopause (16). Reports are available regarding disturbances in sexual hormones following the use of L-carnitine. Fenkci in 2008 showed that decreased total L-carnitine levels may be associated with hyperandrogenism and/or insulin resistance in non-obese women with polycystic ovaries (17).

2. Objectives


Therefore, we designed the present study to investigate any changes in serum levels of testosterone, progesterone and estrogen in cats following ovariohysterectomy after supplementation of L-carnitine to their daily diet. We aimed to characterize whether supplementation of L-carnitine to spayed cats is safe in terms of not altering the sexual hormones.

3. Methods


3.1. Animals

Fourteen adult and healthy female DSH cats, mean weight 3.2 ± 0.3 kg, were selected for the study. The present experimental exploratory study started on 23/1/93 in Tehran/Iran after approval was received from the university research committee, in accordance with the guidelines of its institutional animal experimentation ethics committee No # 302386, 1/12/1384.


3.2. Procedure

The cats were maintained in the same place at ambient room temperature and humidity with a 12h day/night cycle a few days prior to surgery. They were fed with standard laboratory pellets and allowed free access to water. The subjects’ weight was recorded at the beginning of the study. A control blood sample was taken in all cats to measure the serum levels of testosterone, progesterone and estrogen before removal of the gonads. Serum levels of testosterone, progesterone and estrogen were measured with a commercially available AMH enzyme-linked immunosorbent assay (ELISA, DRG, Germany) designed for use with canine and feline samples.


Under general anesthesia and aseptic preparation of the abdomen, conventional midline ovariohysterectomy was performed in all cats. The same surgeon performed all surgeries. Prior to the surgery, the cats were divided into two groups randomly. 10 days after the surgery, in group 2, a single dose of 100 mg/kg L-carnitine (250 mg tablets, Osve, Iran) was supplemented to the regular diet for 50 days. No L-carnitine was added to the diet of group 1. Blood samples were taken from all cats at 10 and 60 days post-operatively. The subjects’ weight was recorded at the end of the study in both groups.


3.3. Statistical Analysis:

Data were summarized as Mean ± SD. A general linear model procedure was used by SAS software version 9.2. Single point measurements, at any particular times, were analyzed using the repeated measure ANOVA, which tests the equality of means between groups across time points while accounting for the correlation between the repeated measures. A P value less than 0.05 was considered statistically significant.

4. Results


All animals survived the surgery and recovered from anesthesia without any complications. Also, no complications were observed following supplementation of L-carnitine in group 2. Mean serum levels of estrogen significantly reduced at 10 days after the surgery in both groups (P = 0.00). Although mean serum levels of progesterone decreased after the surgery in both groups, the changes were not significant (P = 0.78). There was no significant difference in serum level of testosterone prior and after the surgery between the groups. No significant difference was observed in serum levels of estrogen, progesterone and testosterone at 10 and 60 days after the surgery between group 1 and 2 (P > 0.05). Data are illustrated in Table 1.


Table 1.
Mean ± SD of Estrogen, Progesterone and Testosterone in Group Test and Controls at Prior to Surgery, 10 and 60 Days after the Surgery

5. Discussion


The main clinical applications of L-carnitine supplementation are for pets affected with heart disease; ketoacidosis, a serious metabolic consequence of uncontrolled diabetes; and hyperlipidemia. It also appears beneficial in the management of both obesity and fatty liver syndrome in cats (17, 18). Obesity in small animals has emerged as a very important issue over the past decade and is reported to be the most common nutritional disorder identified in veterinary practice. Therefore, weight management remains a challenge for practitioners (19). Neutering is one of the leading causes of weight gain both in dogs and cats. Although ovariohysterectomy is recommended in small animal practice, it is believed that reduction in sex hormones may directly affect the brain through the hormone regulators of food intake and play a role in weight gain following the removal of the ovaries in cats (11, 20). In the proposal of the present study, the subjects’ weight loss during the study was considered as a parameter to measure. Unfortunately, we had many missing data during the experiment, due to challenges in handling the patients and lack of exact information from the owners. Therefore, we could not report the results regarding weight loss. Because this would not affect the objective of the study, we decided to omit this parameter. However, obvious weight loss was observed in cats at the end of the study.


Studies have confirmed a decrease in metabolic rate following ovariohysterectomy in dogs and cats that leads to obesity (21). Mitsuhashi reported significant weight gain in cats following spaying. He defined that the maintenance energy requirement for spayed adult cats is about 25% lower than the cats’ requirement prior to surgery (22). Fat cells can produce estrogen in addition to other sources like the adrenal cortex, liver, brain and skin (23). Because L-carnitine targets fat cells, its effects on sexual hormones that are produced through these tissues after sterilization are relevant. A marked decrease in both estrogen and progesterone would be expected, since basal levels are usually less than 10 pg/mL and 1.0 ng/mL, respectively, after removal of the ovaries. This would happen in 48 hours following the surgery (24, 25). The serum levels of estrogen and progesterone were decreased 10 days after the surgery in both groups in the present study, but there were no significant changes in the parameters after supplementation of L-carnitine between the groups. The results indicated that the addition of L-carnitine in the diet of the cats does not affect the serum levels of estrogen, progesterone and testosterone after ovariohysterectomy. Mustafa et al. conducted the study on ovariectomized rats (26). The rats were gavaged with 100 mg/kg L-carnitine for 60 days. He concluded that the administration of L-carnitine resulted in non-significant changes in serum levels of estrogen in rats. The results of the study are in agreement with the results we obtained in the present study. It has been reported that decreased total L-carnitine levels may be associated with hyperandrogenism in non-obese women with polycystic ovary syndrome (17). We did not observe significant changes in serum levels of testosterone prior and after the surgery between the groups.


Ovariohysterectomy is mainly performed to control population and to prevent estrus and other unwanted behaviors in small animals. However, it is proved to prevent mammary gland tumors and many other sex-hormone-related diseases like pyometra as well (27, 28). Any supplementation to the diet that might affect the production of sex hormones may interfere with the effect of ovariohysterectomy. This may cause the cat to become affected with sex-hormone-related diseases as well as possible demonstration of estrus behavior. However, the lack of influence of L-carnitine on serum levels of estrogen, progesterone and testosterone that was evaluated in this study suggests that L-carnitine can be supplemented to the cats’ diet safely after removal of ovaries. Further studies on sexual hormone disturbances following long-term dietary addition of L-carnitine are recommended.


It is concluded that dietary supplementation of L-carnitine has no effect on serum levels of estrogen, progesterone and testosterone in cats following ovariohysterectomy. Long-term study is recommended.

Acknowledgments

The group of authors would like to thank the research council of the faculty of veterinary medicine, Islamic Azad University, Garmsar Branch for veterinary research on Indigenous domestic animals for their approval and assistance in this research.

References


  • 1. Hagen TM, Liu J, Lykkesfeldt J, Wehr CM, Ingersoll RT, Vinarsky V, et al. Feeding acetyl-L-carnitine and lipoic acid to old rats significantly improves metabolic function while decreasing oxidative stress. Proc Natl Acad Sci U S A. 2002;99(4):1870-5. [DOI] [PubMed]
  • 2. Sunvold GD, Tetrick MA, Davenport GM, Bouchard G. F. . Carnitine supplementation promotes weight loss and decreased adiposity in the canine. In Proceedings. The XXIII World Small Animal Veterinary Association; 1998. 746 pp.
  • 3. Yool DA. Ovarian and uterine surgery, In:Small animal soft tissue surger. London: CABI; 2012. p. 221-41. [DOI]
  • 4. Center SA, Warner KL, Randolph JF, Sunvold GD, Vickers JR. Influence of dietary supplementation with (L)-carnitine on metabolic rate, fatty acid oxidation, body condition, and weight loss in overweight cats. Am J Vet Res. 2012;73(7):1002-15. [DOI] [PubMed]
  • 5. Olson PN, Johnston SD. Animal welfare forum: overpopulation of unwanted dogs and cats. New developments in small animal population control. J Am Vet Med Assoc. 1993;202(6):904-9. [PubMed]
  • 6. Bloomberg MS. Surgical neutering and nonsurgical alternatives. J Am Vet Med Assoc. 1996;208(4):517-9. [PubMed]
  • 7. Stone EA. Ovary and Uterus. In:Slatter D: Text book of small animal surgery. 3 ed. 2. Philadelphia: Saunders; 2003.
  • 8. Morris PJ, Calvert EL, Holmes KL, Hackett RM, Rawlings JM. Energy intake in cats as affected by alterations in diet energy density. J Nutr. 2006;136(7 Suppl):2072S-4S. [PubMed]
  • 9. Towell T. Practical weight management in dogs and cats. United States: Wiley Blackwell; 2011. p. 133-9.
  • 10. Lund EM, Armstrong PJ, Kirk CA, Klausner JS. Prevalence and risk factors for obesity in adult dogs from private US veterinary practices. Int J Appl Res Vet Med. 2006;4(2):177.
  • 11. Jeusette I, Daminet S, Nguyen P, Shibata H, Saito M, Honjoh T, et al. Effect of ovariectomy and ad libitum feeding on body composition, thyroid status, ghrelin and leptin plasma concentrations in female dogs. J Anim Physiol Anim Nutr (Berl). 2006;90(1-2):12-8. [DOI] [PubMed]
  • 12. Center SA. Recent Advances in Canine and Feline Nutrition Volume II: Iams Nutrition Symposium Proceedings. 2. Ohio: Orange Frazer Press; 2003. p. 165-81.
  • 13. Nelson LR, Bulun SE. Estrogen production and action. J Am Acad Dermatol. 2001;45(3 Suppl):S116-24. [PubMed]
  • 14. Sakai K, Fukami K, Yamagishi S, Kaida Y, Adachi T, Ando R, et al. Evidence for a positive association between serum carnitine and free testosterone levels in uremic men with hemodialysis. Rejuvenation Res. 2013;16(3):200-5. [DOI] [PubMed]
  • 15. Cavallini G, Caracciolo S, Vitali G, Modenini F, Biagiotti G. Carnitine versus androgen administration in the treatment of sexual dysfunction, depressed mood, and fatigue associated with male aging. Urology. 2004;63(4):641-6. [DOI] [PubMed]
  • 16. Odo S, Tanabe K, Yamauchi MA. Effects on Weight Management in Healthy Volunteers. 4. Food and Nutrition; 2013.
  • 17. Fenkci SM, Fenkci V, Oztekin O, Rota S, Karagenc N. Serum total L-carnitine levels in non-obese women with polycystic ovary syndrome. Hum Reprod. 2008;23(7):1602-6. [DOI] [PubMed]
  • 18. Blanchard G, Paragon BM, Milliat F, Lutton C. Dietary L-carnitine supplementation in obese cats alters carnitine metabolism and decreases ketosis during fasting and induced hepatic lipidosis. J Nutr. 2002;132(2):204-10. [PubMed]
  • 19. Brooks D, Churchill J, Fein K, Linder D, Michel KE, Tudor K, et al. 2014 AAHA weight management guidelines for dogs and cats. J Am Anim Hosp Assoc. 2014;50(1):1-11. [DOI] [PubMed]
  • 20. Cooke PS, Naaz A. Role of estrogens in adipocyte development and function. Exp Biol Med (Maywood). 2004;229(11):1127-35. [PubMed]
  • 21. German AJ. The growing problem of obesity in dogs and cats. J Nutr. 2006;136(7 Suppl):1940S-6S. [PubMed]
  • 22. Mitsuhashi Y, Chamberlin AJ, Bigley KE, Bauer JE. Maintenance energy requirement determination of cats after spaying. Br J Nutr. 2011;106 Suppl 1:S135-8. [DOI] [PubMed]
  • 23. Jeusette IC, Lhoest ET, Istasse LP, Diez MO. Influence of obesity on plasma lipid and lipoprotein concentrations in dogs. Am J Vet Res. 2005;66(1):81-6. [PubMed]
  • 24. Pineda MH. McDonald's Veterinary Endocrinology and Reproduction. 5 ed. Iowa: Iowa State Univ Pr; 2003.
  • 25. Reece WO. Duke's Physiology of Domestic Animals. 12 ed. New York: Cornell Univ Pr; 2004.
  • 26. Moustafa AM, Boshra V. The possible role of L-carnitine on the skeletal muscle of ovariectomized rats. J Mol Histol. 2011;42(3):217-25. [DOI] [PubMed]
  • 27. Fossum TW. Small Animal Surgery. 4 ed. USA: Elsevier Mosby; 2013.
  • 28. Howe LM. Surgical methods of contraception and sterilization. Theriogenology. 2006;66(3):500-9. [DOI] [PubMed]

Table 1.

Mean ± SD of Estrogen, Progesterone and Testosterone in Group Test and Controls at Prior to Surgery, 10 and 60 Days after the Surgery

Groups Group 1 Group 2
Days
Hormone Prior to Surgery 10 Days After the Surgery 60 Days After the Surgery Prior to Surgery 10 Days After the Surgery 60 Days After the Surgery
Estrogen, pg/mL 18.7 ± 3.2 9.4 ± 1.4a 9.2 ± 2.8 17.4 ± 4.4 8.8 ± 1.7* 7.8 ± 2.5
Progesterone, ng/mL 1.6 ± 0.88 1.2 ± 0.35 1.4 ± 0.68 1.2 ± 0.98 0.91 ± 0,44 0.88 ± 0.32
Testosterone 0.4 ± 0.21 0.5 ± 0.24 0.54 ± 0.33 0.4 ± 0.18 0.4 ± 0.15 0.4 ± 0.21
a Denotes a statistically significant difference within the groups at different measured times.