Evolution of blood parameters during weight loss in experimental obese Beagle dogs

Transcription

1 J. Anim. Physiol. a. Anim. Nutr. 88 (2004), Ó 2004 Blackwell Verlag, Berlin ISSN Receipt of Ms.: Accepted: Animal Nutrition Unit and 2 Biostatistics, Bioinformatics, Economics and Animal Selection, University of Liège, Liège, Belgium and 3 Royal Canin, Centre de Recherches de Aimargues, France Evolution of blood parameters during weight loss in experimental obese Beagle dogs By M. Diez 1,C.Michaux 2,I.Jeusette 1,P.Baldwin 1,L.Istasse 1 and V. Biourge 3 Summary The effects of weight loss on hormonal and biochemical blood parameters were measured monthly [carnitine, creatinine, urea, free T4 (ft4), total T4 (TT4), plasma alkaline phosphatases (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), potassium and total proteins] or bimonthly [cholesterol, triglycerides, non-esterified fatty acids (NEFA), insulin-like growth factor I (IGF-I), glucose, insulin] in eight obese Beagles dogs fed either a high protein dry diet, DP (crude protein 47.5%, on dry matter basis) or a commercial high fibre diet, HF (crude protein 23.8%, crude fibre 23.3%). The dogs were allotted to two groups according to sex and body weight (BW) and they were respectively fed with the DP or the control HF diet during weeks, until they reach their optimal BW. The plasma basal triglycerides and cholesterol concentrations were decreased by the two diets but the difference was only significant for the DP diet. The plasma mean NEFA concentration increased regularly over the period with the HF diet, without significant difference between the two diets. No effect of diet or weight loss was observed on plasma carnitine, urea, creatinine, ALP, AST, ALT, potassium, TT4, FT4, IGF-I, glucose and insulin. Weight loss induced a decrease in ft4 plasma concentration (p < 0.001). The high protein diet allowed a safe weight loss. Introduction Approximately 25% of dogs receiving veterinary care in Western countries are overweight to grossly obese (Edney and Smith, 1986; Armstrong and Lund, 1996). Thus obesity is the most common nutritionally related health problem in companion animals (Sloth, 1992). The most successful approach to weight loss in dogs implies not only a reduction in food intake but also owner compliance and motivation, behavioural changes, physical exercise and follow-up of the animal after the weight loss programme. Whatever the diet chosen, the basis for any weight loss programme is to restrict energy intake in order to induce weight loss while providing all the essential nutrients. Providing high-quality and proper protein level is especially important to minimize losses of fatfree mass. Maintenance of fat-free mass during weight loss represents an important component of successful weight loss (Hannah, 1999). In obese humans fed very low energy diets, increased dietary protein helped maintain lean body mass (Wadden et al., 1985). A clinical trial was described in which a new high protein diet has been offered to Beagle dogs starting a weight loss programme (Diez et al., 2002). The purpose of the study was to evaluate the efficiency of such a diet in clinical and in field conditions. The objective of this U. S. Copyright Clearance Center Code Statement: /2004/ $ 15.00/0

2 Evolution of blood parameters during weight loss in Beagle dogs 167 paper is to present the effects of weight loss or diet on blood parameters in dogs fed either a high protein or a high fibre diet. Materials and methods Eight adult experimental obese Beagles, four neutered males and four intact females, 6 years old (range: 4 7) at the beginning of the study, at least 30% (30 72) overweight for at least 1 year and belonging to the Animal Nutrition Unit were used in this study. All dogs were found to be healthy based on physical examination, complete blood counts, serum chemistry profiles and TSH stimulation tests. Dogs were fed either a high protein, low starch and high fibre dry diet, DP (Table 1) or a commercial high starch and high fibre dry diet, HF during the weight loss programme. The dogs were allotted to two comparable groups according to sex and body weight (BW) before the weight loss programme and they were respectively fed with the DP or the control HF diet during weeks, until they reach their optimal or target BW known from historical data in the colony. Obesity was assessed by the use of body condition scores (Laflamme et al., 1994a). Drinking water was provided ad libitum. The amounts of food were then progressively adjusted to induce a weekly rate of weight loss of around 2% calculated at starting weight. Individual food consumption was recorded daily. Dogs were maintained in their usual kennel, by groups of 2 or 3 during the whole study; each pen was 4 3 m and has a doghouse. The activity level was not measured. Dogs underwent hormonal and biochemical evaluation monthly [carnitine, creatinine, urea, free thyroxine (ft4), total thyroxine (TT4), plasma alkaline phosphatases (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), potassium, total proteins] or bimonthly [cholesterol, triglycerides, non-esterified fatty acids (NEFA), insulin-like growth factor I (IGF-I), glucose, insulin] during the whole study. Blood samples were collected by cephalic venepuncture, centrifuged and kept frozen until analysis (Technicon autoanalyser RA-1000 using triglycerides, cholesterol, glucose and urea reagents from Bayer, Leverkusen, Germany; NEFA by spectrometry with free fatty acids, half microtest, Roche Diagnostics, Germany; insulin, IGF-I, and TT4 with commercial kits from BioSource Europe Fleurus, Belgium). Determinations of ft4 concentrations were performed using a commercial assay kit (ECLIA from Roche). Potassium, AST, ALT, ALP and total proteins were assayed at a commercial laboratory (Laboratoire Collard, Verviers, Belgium). Carnitine was measured by colorimetric method at the laboratory of genetics biochemistry from the university of Liège. The results were Table 1. Nutrient contents and ingredients of the diets fed to obese dogs Diet 1 1 High protein DP Diet 2 2 High fibre HF Moisture Protein (% DM 3 ) Fat (% DM) Ash (% DM) Crude fibre (% DM) Total dietary fibre (% DM) Metabolizable energy as fed (kj/g) High protein experimental diet. Ingredient list: poultry meal, corn gluten, rice gluten, purified cellulose, barley, beet pulp, poultry fat, poultry liver hydrolisate, minerals, psyllium seeds, brewer s yeasts, fructooligosaccharides, chelated trace elements, l-carnitin and vitamins 2 Hill s Prescription Diet, Canine R/D dry, Hill s Pet Nutrition, Topeka, KS 3 DM, dry matter 4 Energy content was measured at the Research Center of Royal Canin, France

3 168 M. Diez et al. analysed by SAS Mixed Procedure (SAS Institute, Cary, NC, USA) for longitudinal data with treatment (diet) and sex as fixed effects. Data are presented in the text, figure and table as mean ± SEM. The protocol was approved by the Animal Use and Care Advisory Committee of the University of Liège. Results The two groups of dogs reached their optimal BW within weeks for the HF diet and weeks for the DP diet, with no significant difference between the duration of the weight loss programme. The energy levels that induced weight loss corresponded, respectively for DP and HF diets, to 76 68% of the maintenance energy requirement (MER) for optimal body weight, on the assumption that 550 kj kg (0.75) can be considered as an adequate equation to estimate daily MER in medium-sized adult dogs. Before weight loss, plasma triglycerides and cholesterol concentrations were respectively in normal ranges (Table 2). The two diets decreased the plasma concentrations of these two metabolites but the difference was only significant for the DP diet. The basal plasma mean NEFA concentration was 0.40 ± 0.03 mmol/l and increased regularly over the period with the HF diet. No effect of diet was observed on plasma carnitine, urea, creatinine, ALP, AST, ALT, potassium, TT4, ft4, IGF-I, glucose, insulin, potassium, total proteins, which remained constant and in normal ranges over the weight loss period. Blood urea and IGF-I concentrations were significantly higher for the females than for males during the whole weight loss period (p < 0.05). Weight loss induced a decrease of ft4 plasma concentration with the two diets (p < 0.001). Mean plasma concentration of ALP was higher in males than in females (p < 0.05). Table 2. Plasma metabolites profiles of two groups of obese Beagles receiving a high protein or a high fibre diet 1 Pre-restriction Post-restriction DP 2 HF 2 DP HF Triglycerides (mmol/1) 0.59 ± ± ± 0.07*, ± Cholesterol (mmol/l) 5.56 ± ± ± 0.49*, ± NEFA 2 (mmol/l) 0.36 ± ± ± ± 0.03 IGF-I 2 (mmol/l) 156 ± ± ± ± 58 Glucose (mmol/l) 5.00 ± ± ± ± 0.33 Insulin (pmol/l) 80.4 ± ± ± ± 11 Carnitine (lmol/l) 22.3 ± ± ± ± 2.4 Creatinine (lmol/l) 65.4 ± ± ± ± 5.3 Urea (mmol/l) 5.0 ± ± ± ± 0.6 ft4 2 (nmol/l) 1.44 ± ± ± 0.13** 0.97 ± 0.11** TT4 2 (nmol/l) 23.0 ± ± ± ± 2.7 ALP 2 (UI/l) 127 ± ± ± ± 31 AST 2 (UI/l) 20.3 ± ± ± ± 3.3 ALT 2 (UI/l) 38.4 ± ± ± ± 16.0 Potassium (meq/l) 4.9 ± ± ± ± 0.1 Total proteins (g/l) 62.8 ± ± ± ± All values are mean ± SEM 2 Abbreviations: NEFA, non-esterified fatty acids; IGF-I, insulin-like growth factor I; ft4, free thyroxine; TT4, total thyroxine; ALP, alkaline phosphatases; AST, aspartate aminotransferase; ALT, alanine aminotransferase 3 Change with weight loss significantly different between diets (p < 0.05) Significant change following weight loss (*p < 0.05, **p < 0.01)

4 Evolution of blood parameters during weight loss in Beagle dogs 169 Discussion The effect of diet on blood parameters has not been reported extensively in dogs. Although we had a small number of dogs in each group, statistical analysis allowed to distinguish the differences between diets or the effects of weight loss on blood parameters. If the effects induced by the two diets were similar, the experiment did not allow to distinguish between the effects of diets or weight loss by itself. When the effects of diets were similar, we described the effects of weight loss only. Meanwhile, the effects of diets were very limited. According to some authors, obese dogs present high levels of plasma glucose and insulin, which are sometimes referred to as intolerance to glucose and hyperinsulinaemia (Mattheeusws et al., 1984). Although the dogs were grossly obese for more than 1 year, the fasting glucose and insulin plasma concentrations were in normal ranges and similar between diet groups prior to the period of energy restriction, and were not significantly affected during the whole study in either of the two diet groups. This was previously reported in a similar experiment but the authors hypothesized that glucose and insulin concentrations were unchanged because the dogs were not grossly obese prior to the energy restriction (Borne et al., 1996). The observed changes in cholesterol profiles following weight loss with DP diet could have been due to a number of factors. Energy restriction alone may affect lipid concentrations. But in this hypothesis, the cholesterol-lowering effect would have been significant with both diets, which is not the case. The effects of diets containing dietary fibres on plasma cholesterol concentration have been reported extensively in healthy or in hyperlipidaemic dogs. By contrast, the effects of dietary fibres are more limited on triglycerides concentrations. Hyperlipidaemia is not reported in a systematic way in obese dogs although obese client-owned dogs could present slight elevation of blood lipids, mainly due to the diet offered. The dogs used in the present trial did not present elevated blood lipids concentrations before the weight loss programme. The mean value and SEM in HF diet were much higher compared with DP before restriction. After restriction, the mean reduction is higher in HF compared with DP, but the reduction is significant only in DP probably because of the high variation in HF. The DP diet contained high amounts of total dietary fibres and induced significant decreases of both triglycerides and cholesterol concentrations during the course of the weight loss programme. However, this hypolipidaemic effect should be mainly attributed to the high concentrations of total both insoluble and soluble dietary fibres in the DP diet and not to the low fat concentrations, which were quite similar for the two diets. Furthermore, the DP diet contained 1% added short chain fructooligosaccharides, which are known for their cholesterol-lowering effect either in healthy or in hyperlipidaemic dogs (Diez et al., 1997, 2000). The increase of NEFA concentration during the weight loss programme has to be attributed to the mobilization of fat from adipocyte following the restricted energy. Fasting or weight loss has been reported to decrease thyroid hormone concentrations in humans and rats. Similar data in dogs regarding possible effects of energy restriction on thyroid function test results are scarce, with the exception of a decrease of T3 reported in one study, in relation to the degree of energy restriction (Laflamme et al., 1994b). The measurement of ft4 is thought to be interesting because it is less influenced by nonthyroidal diseases than determination of TT4 (Scott-Moncrieff and Guptill-Yoran, 2000). Although our dogs were found to be euthyroid following a TSH stimulation test prior to the energy restriction, the decreased concentration of ft4 during the course of the weight loss programme reflects a general decrease of the metabolism. This seems logical regarding the average energy allowance that has to be regularly decreased to ensure a 1 2% weekly weight loss rate (Diez et al., 2002). Serum IGF-I concentration is generally considered as a biochemical marker of nutritional status and correlates significantly with BW in cats and dogs (Eigenmann et al., 1984; Maxwell et al., 1999). Because normally IGF-I levels reflect the growth

5 170 M. Diez et al. hormone (GH) status and because GH secretion is decreased in obesity, it has been suggested that IGF-I is stimulated by the hyperinsulinism that is very often present in the obese state (Clemmons and van Wyk, 1984). Furthermore, IGF-I is reduced by fasting or by short-term dietary restriction in cats (Maxwell et al., 1999). In the present trial, we did not observe significant variations of IGF-I, nor insulin concentrations during the weight loss programme. One could presume that high individual variations of these two metabolites along with the reduced size of the samples (four dogs for each group) could explain the lack of significant result. Renal function was checked with measurements of blood urea and creatinine. Blood urea was higher in the DP group once DP was given to the dog, and this was observed during the whole study, although not reflected by the figures presented in Table 2. As DP contained 47.5% protein vs. 23.8% dry matter basis for HF and as blood urea in the dog is clearly linked to the protein concentration, this observation was expected. However, the concentrations both in the DP and in the HF group were in normal ranges during the whole study. Using sex as a fixed effect in our statistical analysis allowed us to assess a difference of energy allowance between males and females to induce and maintain constant weight loss (data not shown). This is important to establish the feeding plan of obese dogs and especially obese females but it also showed significant differences between males and females for some blood parameters. For ALP, the basal concentration was higher in males than females before the study. As the excess weight was similar in both sexes, we considered the other Ôsexes effectsõ as fortuitous. In conclusion, there was only an effect of diet on plasma cholesterol and triglycerides. Weight loss induced significant decreases of plasma cholesterol, triglycerides and ft4, irrespectively of the diet offered. The high protein diet allowed a safe weight loss in the DP group. It is therefore interesting to check blood parameters of dogs before a weight loss programme. This could be made as a routine examination to verify that obese dogs do not suffer from endocrinopathies as hypothyroidism, diabetes mellitus or hyperadrenocorticism. But, it could be checked again, for example, at the mid-time or at the end of the weight loss programme to control renal or liver function, especially because the prevalence of obesity is high in senior dogs. References Armstrong, P. J.; Lund, E. M., 1996: Vet. Clin. Nutr. 3, 83. Borne, A. T.; Wolfsheimer, K. J.; Truett, A. A.; Jiene, J.; Wojciechowski, T.; Davenport, D. J.; Ford, R. B.; West, D. B., 1996: Obes. Res. 4, 337. Clemmons, D. R.; van Wyk, J. J., 1984: Clin. Endocrinol. Metab. 3, 113. Diez, M.; Hornick, J. L.; Baldwin, P.; Istasse, L., 1997: Am. J. Vet. Res. 58, Diez, M.; Grauwels, M.; Jeusette, I.; Tonglet, C.; Istasse, L., 2000 Short-chain fructooligosaccharides (SC-FOS) in hyperlipidaemic dogs. Proceedings of Dietary fibre 2000, Dublin, Ireland, May 2000, p Diez, M.; Nguyen, P.; Jeusette, I.; Devois, C.; Istasse L.; Biourge, V., 2002: J. Nutr. 132, 1685S. Edney, A. T. B.; Smith, P. M., 1986: Vet. Rec. 118, 391. Eigenmann, J. E.; Patterson, D. F.; Froesch, E. R., 1984: Acta Endocrinol. 106, 448. Hannah, S., 1999: Comp. Cont. Educ. Pract. Vet. 21, 32. Laflamme, D. P.; Kealy, R. D.; Schmidt, D. A., 1994a: J. Vet. Int. Med. 8, 154. Laflamme, D. P.; Kuhlman, G.; Lawler, D. F.; Kealy, R. D.; Schmidt, D. A., 1994b: Vet. Clin. Nutr. 1, 59. Mattheeusws, D.; Rottiers, R.; Bayens, D.; Vermeulen, A., 1984: J. Am. Anim. Hosp. Assoc. 20, 287. Maxwell, A.; Butterwick, R.; Batt, R.M.; Camacho-Hubner, C., 1999: J. Nutr. 129, 1879.

6 Evolution of blood parameters during weight loss in Beagle dogs 171 Scott-Moncrieff, C. R.; Guptill-Yoran, L., 2000: Hypothyroidism. In: Ettinger, E. J. and Feldman, E. C. (eds), Textbook of Veterinary Internal Medicine, 5th edn. W.B. Saunders, Philadelphia, PA, pp Sloth, C., 1992: J. Small Anim. Pract. 33, 178. Wadden, T. A.; Stunkard, A. J.; Brownell, K. D.; Day, S.C., 1985: Am. J. Clin. Nutr. 41, 533. Author s address: Marianne Diez, Animal Nutrition Unit, Animal Production Department, B43 Faculty of Veterinary Medicine, Boulevard de Colonster, 20, University of Liège, B-4000 Liège, Belgium, mdiez@ulg.ac.be