Obesity and the resulted adverse effects such as cardiovascular diseases and increased rate of morbidity and mortality are problems resulting from changes in life habits and indus-trlization, however, weight variations as obesity or leanness sometimes are signs of a serious disease and need serious attention, too. Wasting can result from certain cancers such as pancreas and other gastrointestinal malignancies [1, 2]. Many factors in human body are involved in weight regulation. Neuropeptide Y, serotonine, glucagon like peptide 1, tumor necrosing factor-α (TNF-α) and some hormones like insulin and leptin are some of these regulators [3, 4]. TNF-α induces weight loss by increasing catabolism of adipose and muscle cells, loss of appetite and inhibition of synthesis of lipoprotein lipase. Lipoprotein lipase is essential to release of fatty acids from lipoproteins circulating in blood flow to be used by tissues .
Some medicines such as histamine receptor (H1) blockers can affect weight regulation mechanisms and cause weight changes. Cyproheptadine is one of the most administered drugs for appetite increase and weight gain in people who suffer from strong weight loss . Recently, cyproheptadine has been accepted as an appetite stimulator in catexia [7, 8].
Ketotifen is a potent, safe and long acting antihistamine that is effective in treatment of asthma and taking this drug causes weight gain and drowsiness in human beings . Some studies suggest that ketotifen inhibits the release of TNF-α from mono nuclear cells of peripheral blood stream. Administration of ktotifen to patients with acquired immune deficiency syndrome (AIDS) who have elevated levels of TNF-αcauses improvement of their disease, reduction (14%) of TNF-α level, and weight gain about 11-12 Lb in less than 4 weeks [10, 11].
Antihistamines (H1-blockers) are administered for their antihistaminic effects to control allergic reactions, but in some cases their side effects such as appetite increase and weight gain are the aim of their administration. In the present study, we investigated the effect of different doses of ketotifen on the appetite and weight changes in mice and compared it with the effect of cyproheptadine, a well recognized drug with similar effects.
2. Materials and methods
Pure powders of ketotifen and cyproheptadine were obtained from Hakim and Darupaksh Pharmaceutical Companies, Tehran, Iran, respectively. The powders were dissolved in sodium chloride solution and the determined doses of them were injected subcutaneously to the mice.
2.2 Animals and treatment
Male mice (body weight 20-23 g) were used for this study. They were allowed access to water and food ad libitum. The animals were divided into eight groups of eight mice each and received the following treatments for 45 days. Group I was control group and received normal saline (s.c.) during study. Three groups (II-IV) received three different doses of ketotifen (8, 16 and 32 mg/kg, s.c.). Three other groups (V-VII) treated with three doses of cyproheptadine (5, 10 and 20 mg/kg, s.c.). The eighth group (VIII) received ketotifen (8 mg/kg) and cyproheptidine (5 mg/kg) simultaneously by one s.c. injection. Diet intake was measured daily and body weight (BW) was recorded every 2 days.
2.3. Statistical analysis
The data were expressed as the mean ± SE of eight mice in each group and statistical comparisons were made with the Student's t-test, and p< 0.05 were considered significant.
3.1. Effect of different doses of cyproheptadine on the weight and appetite of mice
Cyproheptadine at the lowest dose used (5 mg/kg) caused a weight gain, but higher doses did not. The 10 mg/kg dose did not cause a significant weight gain, and the 20 mg/kg dose even caused a weight loss compared to the control group (p < 0.01 ) Effect of cyproheptadine on appetite of mice is represented as the amount of consumed diet in Figure 2. The results show that the low dose of cyproheptadine (5 mg/kg) caused a significant increase in food intake in mice ( p < .001 ) , but the 10 mg/kg dose of it did not significantly affect the food intake, and the 20 mg/kg dose resulted in a significant decrease in food intake ( p < 0.05).
Figure 1. Weight change caused by different doses of cyproheptadine administered (s.c.) in mice for 45 days. Values represent the Mean±SE of 8 animals per group. Significantly different from the control group;
* p< 0.05, **p < 0.01, p < 0.005.
Figure 2. Changes in food intake caused by different doses of cyproheptadine administered (s.c.) in mice for 45 days. Values represent the Mean±SE of 8 animals for per group. Significantly different from the control group; *p < 0.05, p < 0.005.
3.2. Effect of different doses of ketotifen on weight and appetite of mice
Ketotifen caused a significant weight gain in mice and this increase in weight was dose dependent (Figure 3). Day to day comparison of the weight change in mice during 45 days of administration shows that injection of ketotifen with a dose of 16 mg/kg does not significantly change the weight of mice compared to the control group, but with a dose of 32 mg/kg significantly increased weight, especially during days 20 to 45 of the experiment (Figure 3). As shown in Figure 4, only the highest dose of ketotifen used (32 mg/kg) caused a significant increase in food intake( p < 0.01).
Figure 3. Weight change caused by different doses of ketotifen administered (s.c.) in mice for 45 days. Values represent the Mean±SE of 8 animals per group. Significantly different from the control group; * p < 0.05
Figure 4. Changes in food intake caused by different doses of ketotifen administered (s.c.) in mice for 45 days. Values represent the Mean±SE of 8 animals per group. Significantly different from the control group;**p < 0.05.
3.3. Effect of co-administration of ketotifen and cyproheptadine on weight and appetite of mice
Results presented in Figure 5 suggest that co-administration (s.c.) of ketotofen (8 mg/kg) and cyproheptadine (5 mg/kg) causes less weight gain than either of the two administered alone (p < 0.01). The mean of food intake during 45 days of study in mice received co-administration of ketotifen and cyproheptadine was significantly higher than in mice received ketotifen alone ( p < 0.01) and lower than in mice received cyproheptadine alone (p < 0.01) in similar doses (Figure 6).
Figure 5. Weight change caused by cyproheptadine, ketotifen and their co-administration (s.c.) in mice for 45 days. Values represent the Mean±SE of 8 animals per group. Significantly different from co-administration group; *p< 0.05, p < 0.01, p < 0.005
Figure 6. Changes in food intake caused by cyproheptadine, ketotifen and their co-administration (s.c.) in mice for 45 days. Values represent the Mean±SE of 8 animals per group. Significantly different from co-administration group; ** p < 0.01.
Ketotifen is a safe antihistamine administered extensively to the patients, however, appetite stimulation and weight gain are its common side effects in human [12, 13]. Ketotifen inhibits release of TNF-α from mononuclear cells in blood . TNF-α causes weight loss through increasing catabolism of fat and muscular cells. It is believed that anorexia created by TNF-αis the main cause of weight loss. Also, TNF-α inhibits the synthesis of lipoprotein lipase .
Cellular infection associated by HIV causes secretion of many cytokines that create different signs of AIDS. TNF-α is one of the most important cytokines which cause spreading of viruses and contamination of T-cells and lymphatic glands. It seems that TNF-αis in correlation with wasting acquired in AIDS . Inhibition of release of TNF-α from mononuclear cells in blood by ketotifen probably helps in treating the malnutrition resulted from HIV.
As shown in some studies, administration of ketotifen to patients with AIDS who had higher levels of TNF-α resulted in improvement of the disease process, 14% reduction in TNF-α levels and 11-12 pound weight gain during lees than 4 weeks [11, 15]. Ketotifen also has been reported to cause a significant weight gain in children with asthma during treatment of their disease . In the present study, however, injection of different doses of ketotifen showed different results in mice, and the high doses of ketotifen caused a significant weight gain, compared to the control group, while the low doses resulted in a significant weight loss. These results suggest that different doses of ketotifen may act through different mechanisms and may show different results in different patients. However, mechanisms may be different in human and mice, as well.
Cyproheptadine is an antihistamine with strong anticholinergic and antiserotonergic effects [17, 18]. It has been used for the treatment of anorexia and weight loss associated with cystic fibrosis and has shown stimulation of appetite . Also cyproheptadine is used successfully in treatment of serotonin syndrome and caused an increase in appetite and weight gain .
The possible reasons for appetite stimulation and weight gain by cyproheptadin are: 1) inhibition of 5-HT2A receptors, 2) reduction in gastrointestinal tract motility and subsequently increasing transit time of food, due to anticholinergic effects of the drug, and 3) drowsiness and hypoactivity and storage of excess calories .
The results obtained by different doses of cyproheptadine (5, 10 and 15 mg/kg) in mice in the present study showed a significant weight gain by low dose while high dose of cyproheptadine caused a significant weight loss. The weight gain caused by low dose of cyprohptadine shows that this drug increases the appetite and feeding at low doses. Medium dose of cyproheptadine used in this study (10 mg/kg) resulted in weight gain without a significant increase in feeding. The probable reason for this result is anticholinergic, tranquilizer and sedative effects of cyproheptadine. On the other word, at this dose, drug does not stimulate appetite strongly, but reduces GI motility and animal activity and increases transit time of food. High dose of cyproheptadine (20 mg/kg) caused weight loss without a significant reduction in feeding in animals. The different results by variable doses of cyproheptadine suggest different mechanisms of action with different doses.
Administration of ketotifen (8 mg/kg) and cyproheptadine (5 mg/kg) simultaneously in one injection compromises the effects of these drugs when administered separately. That is, in this position the weight gain is greater than ketotifen and less than cyproheptadine, when given alone. This is to say that in long term use, weight gain by cyproheptadine has been overcome to weight loss caused by ketotifen. Finally, it can be concluded from this study that probably appetite stimulating effects of ketotifen appears to be dose dependent and appears with delay. Probably administration of these two drugs at the same time can help to overcome the appetite stimulating effects of cyproheptadine where this effect is unpleasant. Of course, more studies are needed to confirm this result.