Plasma leptin concentrations in cats: reference range, effect of weight gain and relationship with adiposity as measured by dual energy X-ray absorptiometry

The aims of our study were to determine a reference range for plasma leptin in healthy, normal-weight cats and to measure the effect of weight gain on plasma leptin levels. To increase our understanding of the association between leptin and feline obesity, we investigated the relationship between plasma leptin and measures of adiposity in cats. Twenty-six normal-weight cats were used to determine the reference range for feline leptin using a multispecies radioimmunoassay. In the second part of the study, plasma leptin concentrations were determined in 16 cats before and after approximately 10 months of spontaneous weight gain. Dual energy X-ray absorptiometry scans (DEXA) were performed after weight gain. The tolerance interval for plasma leptin concentrations was 0.92-11.9 ng/ml Human Equivalent (HE) with a mean concentration of 6.41+/-2.19 ng/ml HE. In part two of the study, 16 cats gained on average 44.2% bodyweight over 10 months. The percentage of body fat in obese cats ranged from 34.2 to 48.7%. Mean plasma leptin concentrations increased from 7.88+/-4.02 ng/ml HE before weight gain to 24.5+/-12.1 ng/ml HE after weight gain, (P<0.001). Total body fat and body fat per cent were the strongest predictors of plasma leptin in obese cats (r=0.8 and r=0.78, P<0.001, respectively). In conclusion, plasma leptin concentrations increased three-fold in cats as a result of weight gain and were strongly correlated with the amount of adipose tissue present. Despite elevated leptin levels, cats continued to eat and gain weight, suggesting decreased sensitivity to leptin. This investigation into the biology of leptin in cats may aid the overall understanding of the role of leptin and the development of future treatments to help prevent and manage feline obesity.     

Variations of plasma leptin in show horses during a work season

Leptin is an adipocytokine mainly expressed by adipose tissue. Secretion of leptin in healthy animals is closely related to fat mass and metabolic activity. The aim of this study was to investigate plasma leptin variations, in relation to nutritional and exercise parameters in adult show horses during a work season. EDTA-blood samples were taken at rest from 37 Iberian horses. Body weight, body condition score and fat percentage determined by ultrasonic measurement of rump fat thickness were measured. Plasma leptin was determined with a multi-species RIA kit. Linear mixed effects model was used to assess relationship between plasma leptin and other biological parameters. Plasma leptin concentration was <12.6 ng/ml (mean = 2.8 ± 1.6 ng/ml) and was significantly higher during training periods (p < 0.0001) (4.5 ± 1.7 ng/ml) than in show periods (2.0 ± 1.1 ng/ml), despite a significant increase (p < 0.0001) in energy intake. The body weight remained almost constant. The plasma leptin concentrations were significantly affected by exercise (p < 0.0001), body weight (p = 0.04) and BCS (p < 0.0001), but were not affected by percentage of fat. In conclusion, the marked decrease in leptin values observed during a period of intense (i.e. excessive) exercise could result from an adaptation to cumulative alterations in energy balance, to exercise per se or to a combination of both.     

Leptin, body fat content and energy expenditure in intact and gonadectomized adult cats: a preliminary study

The present study was conducted to assess the body composition, leptin, and energy expenditure changes following gonadectomy in cats. Twenty-one females (12 intact and nine spayed) and 21 males (11 intact and 10 castrated) were used. Body weight was recorded. Serum plasma leptin was measured by radioimmunoassay and body composition and energy expenditure were assessed after injection of doubly labelled water. These results confirmed the gain in body weight and body fat following neutering and demonstrated a strong linear relationship between body fat and serum level of leptin. Energy expenditure decreased in castrated cats in comparison with intact ones. This study underlined the effect of gonadectomy as a major factor of obesity in cats and showed that the increase in circulating leptin reflected the amount of body fat. The present results provide further evidence that the regimen of gonadectomized cats should be carefully controlled to avoid excessive weight gain.     

Effect of omega-3 polyunsaturated fatty acids and body condition on serum concentrations of adipokines in healthy dogs

Objective-To determine associations between serum concentrations of omega-3 polyunsaturated fatty acids or body condition and serum concentrations of adiponectin, leptin, insulin, glucose, or triglyceride in healthy dogs. Animals-62 healthy adult client-owned dogs. Procedures-Body condition score and percentage of body fat were determined. Blood samples were collected after food was withheld for 12 hours. Serum was harvested for total lipid determination, fatty acid analysis, and measurement of serum concentrations of adiponectin, leptin, insulin, glucose, and triglyceride. Associations between the outcome variables (adiponectin, leptin, insulin, glucose, and triglyceride concentrations) and each of several variables (age, sex, percentage of body fat, and concentrations of total lipid, α-linolenic acid, eicosapentaenoic acid, docosapentaenoic acid, and docosahexaenoic acid) were determined. Results-Serum concentrations of docosapentaenoic acid were significantly positively associated with concentrations of adiponectin and leptin and negatively associated with concentrations of triglyceride. Serum concentrations of α-linolenic acid were significantly positively associated with concentrations of triglyceride. No significant associations were detected between serum concentrations of eicosapentaenoic acid or docosahexaenoic acid and any of the outcome variables. Percentage of body fat was significantly positively associated with concentrations of leptin, insulin, and triglyceride but was not significantly associated with adiponectin concentration. Age was positively associated with concentrations of leptin, insulin, and triglyceride and negatively associated with concentrations of adiponectin. Sex did not significantly affect serum concentrations for any of the outcome variables. Conclusions and Clinical Relevance-Docosapentaenoic acid may increase serum concentrations of adiponectin and leptin and decrease serum triglyceride concentration in healthy dogs.     

Treatment of feline diabetes mellitus using an alpha-glucosidase inhibitor and a low-carbohydrate diet

The purpose of this study was to determine the effect of an alpha-glucosidase inhibitor (acarbose), combined with a low-carbohydrate diet on the treatment of naturally occurring diabetes mellitus in cats. Eighteen client-owned cats with naturally occurring diabetes mellitus were entered into the study. Dual-energy X-ray absorptiometry (DEXA) was performed prior to and 4 months after feeding the diet to determine total body composition, including lean body mass (LBM) and percent body fat. Each cat was fed a commercially available low-carbohydrate canned feline diet and received 12.5mg/cat acarbose orally every 12h with meals. All cats received subcutaneous insulin therapy except one cat in the study group that received glipizide (5mg BID PO). Monthly serum glucose and fructosamine concentrations were obtained, and were used to adjust insulin doses based on individual cat's requirements. Patients were later classified as responders (insulin was discontinued, n=11) and non-responders (continued to require insulin or glipizide, n=7). Responders were initially obese (>28% body fat) and non-responders had significantly less body fat than responders (<28% body fat). Serum fructosamine and glucose concentrations decreased significantly in both responder and non-responder groups over the course of 4 months of therapy. Better results were observed in responder cats, for which exogenous insulin therapy was discontinued, glycemic parameters improved, and body fat decreased. In non-responders, median insulin requirements decreased and glycemic parameters improved significantly, despite continued insulin dependence. The use of a low-carbohydrate diet with acarbose was an effective means of decreasing exogenous insulin dependence and improving glycemic control in a series of client-owned cats with naturally occurring diabetes mellitus.     

Influence of a high-protein diet on energy balance in obese cats allowed ad libitum access to food

The influence of a high-protein [HP, 47% of metabolizable energy (ME)] diet on energy balance was evaluated in obese cats allowed ad libitum access to food. Energy intake, body weight, body composition, energy expenditure, and concentrations of hormones and metabolites associated with carbohydrate and lipid metabolism (glucose, insulin, free fatty acids, triglycerides and leptin) were measured in cats after consuming either a moderate protein (MP, 27% of ME) or HP diet for 4 months. Indirect respiration calorimetry showed that resting and total energy expenditure (kJ/day) adjusted for either body weight or lean body mass was increased in cats consuming the HP in relation to MP diets. However, voluntary energy intake also was increased in the HP treatment and, thus, there was no difference in body weight between animals consuming the two diets. Body composition measurements using deuterium oxide dilution showed that dietary protein content did not alter amounts of either lean body mass or fat mass. No significant differences (p > 0.05) were observed between the two treatment groups for blood glucose, free fatty acid or leptin concentrations, although there was a trend (p = 0.054) towards an increase of serum insulin concentrations in the cats eating the HP diet. This study showed that short-term ad libitum feeding of an HP diet did not reduce food intake or promote weight loss in obese cats. However, energy expenditure was increased in the HP diet group and it is possible that this effect of HP might help promote weight loss when energy intake is restricted.     

Fat mass,and not diet,has a large effect on postprandial leptin but not on adiponectin concentrations in cats

Leptin and adiponectin play important roles in carbohydrate and lipid metabolism in different species. Information is limited on the effects of diet, weight gain, and fat mass on their concentrations in cats. This study compared fasting and postprandial blood leptin and total adiponectin concentrations before and after 8 wk of ad libitum feeding to promote weight gain in adult cats (n = 32) fed either a low-carbohydrate, high-protein (23% and 47% ME) or a high-carbohydrate, low-protein (51% and 21% ME) diet. There were significant effects of total, abdominal, and nonabdominal fat mass, but not diet or body weight, on mean 24-h and peak leptin (P < 0.01); observed increases in mean and peak leptin were greatest for abdominal fat mass (50% and 56% increase for every extra 100 g, respectively). After weight gain, postprandial leptin concentration increased markedly relative to when cats were lean, and the duration of the increase was longer after a mean weight gain of 37% with the low-carbohydrate, high-protein diet group compared with 17% with the high-carbohydrate, low-protein group (P ≤ 0.01). Adiponectin was lower than fasting at some time points during the postprandial period in both groups (P ≤ 0.05). For both fasting and mean 24-h adiponectin, there was no significant diet effect (P ≥ 0.19) or changes in weight gain relative to when cats were lean (P ≥ 0.29). In conclusion, fat mass, and not diet, has a large effect on postprandial leptin but not adiponectin concentrations in cats.     

Serum neuropeptide Y (NPY) and leptin concentrations in pigs selected for components of efficient lean growth

Responses in log transformed serum neuropeptide Y (NPY) concentration and leptin concentration after six generations of divergent selection on components of efficient lean growth in pigs were measured. From an animal breeding perspective, serum NPY and/or leptin concentrations could be used as physiological predictors of genetic merit if there were significant responses to selection. At 90 kg liveweight, log transformed serum NPY concentrations were increased with divergent selection for low food conversion ratio (LFC) (6.31 versus 5.72, SED 0.09 log(pmol/L)) or for high lean growth rate (LGA) (5.80 versus 5.37 log(pmol/L)) but not with selection on daily food intake (DFI) (6.26 versus 6.14 log(pmol/L)). Selection for high DFI was associated with increased serum leptin concentration (3.06 versus 2.45, SED 0.21 ng/mL human equivalent (HE)) as was selection for low LFC (3.04 versus 2.46 ng/mL HE). Correlations between leptin and predicted lipid weight increased with stage of test (0.13, 0.34 and 0.43, SE 0.08 at 30, 50 and 75 kg). The high correlations between successive serum NPY concentrations (0.80, SE 0.11) suggest that changes in body composition with time would not be reflected in serum NPY concentrations. Serum NPY and, to a lesser extent, serum leptin concentrations were insensitive to dietary differences in total lysine: energy and indicated that studies using a genetic resource population of animals may be more powerful than nutritional studies using isoenergetic diets differing in lysine content to examine aspects of function of serum concentrations of NPY and leptin in pigs.     

Maternal expression of functional lipoprotein lipase and effects on body fat mass and body condition scores of mature cats with lipoprotein lipase deficiency

OBJECTIVE: To assess effects of deficiency of lipoprotein lipase (LPL) on body condition scores and lean and fat body masses of adult cats. ANIMALS: 12 cats without LPL mutations and 23 cats that were heterozygous or homozygous carriers of the Gly412Arg LPL mutation. PROCEDURE: Lean and fat body masses were estimated by use of body condition scores and change in enrichment of serum after IV administration of deuterium oxide. Mass spectroscopy and infrared absorbance methods were used to determine deuterium enrichment. RESULTS: Fat body mass (mean +/- SD; 0.2 +/- 0.1 kg) and percentage body fat (6.2 +/- 1.4%) of homozygotes were significantly less than those of clinically normal cats and heterozygotes (0.7 +/- 0.1 kg, 18.2 +/- 1.6% and 0.5 +/- 0.1 kg, 15.6 +/- 1.7%, respectively). Homozygous offspring of homozygous dams had significantly less fat body mass (0.1 +/- 0.1 kg) and percentage body fat (2.1 +/- 1.0%) than homozygous offspring of heterozygous dams (0.3 +/- 0.1 kg and 9.2 +/- 1.7%, respectively). Lean body mass did not differ significantly among groups. For all groups, percentage body fat was significantly correlated with body condition score (r= 0.65), and body condition scores supported findings for fat body mass. CONCLUSIONS AND CLINICAL RELEVANCE: Deficiency of LPL activity in cats diminishes stores of body fat. This is consistent with a low rate of de novo synthesis of fat. The effect of dam on body masses in mature LPL-deficient cats indicates nutrient programming of adipose formation during gestation or lactation.     

Obesity increases initial rate of fibrin formation during blood coagulation in domestic shorthaired cats

Obesity predisposes to a prothrombotic state in humans, but whether a similar state occurs in obese animals is unknown. The objective of the current study was to examine the effect of body fat percentage (BF) on haemostatic parameters including thromboelastography with tissue factor as activator (TF-TEG) in client owned indoor-confined physically inactive cats. Seventy-two cats were included following an initial thorough health examination, and a complete blood count, biochemistry panel, conventional coagulation panel and a TF-TEG analysis were performed with tissue factor (1:50,000) as activator. The cats were anaesthetized, and BF was measured using Dual-energy X-ray absorptiometry. Significant difference between lean (BF < 35%, n = 26), overweight (35% < BF < 45%, n = 28) and obese (BF > 45%, n = 18) cats was identified using ANOVA. The correlation between BF, serum leptin and total adiponectin, respectively, with individual TEG and conventional coagulation parameters was evaluated. Obese cats showed a faster rate of fibrin formation (TF-TEG(R), p < 0.05), and TF-TEG(R) was positively correlated with plasma leptin levels. Increasing BF did not affect other conventional coagulation or TF-TEG parameters. In conclusion, this study indicates a connection between body fat content and altered haemostasis, also in cats. Whether feline obesity causes a hypercoagulable state of clinical relevance should be further investigated.     

Serum concentrations of leptin in six genetic lines of swine and relationship with growth and carcass characteristics

The objective of this study was to evaluate the relationship between serum concentrations of the hormone leptin with growth and carcass traits insix distinct breeds of pigs entered into the 2000 National Barrow Show Sire Progeny Test. Breeds evaluated were Berkshire (n = 131), Chester White (n = 33), Duroc (n = 40), Landrace (n = 23), Poland China (n = 26), and Yorkshire (n = 41). Serum samples were collected and assayed for concentrations of leptin at entry into test (On-Test Leptin) at 34 +/- 6.7 kg of live weight and again 24 h prior to harvest (Off-Test Leptin) at 111 +/- 3.1 kg of live weight. Carcass measurements taken included hot carcass weight, carcass length, backfat, longissimus muscle area (LMA), longissimus pH, Hunter L-value, chemically determined intramuscular fat (IMF), and subjective color, marbling, and firmness scores. Average daily gain, IMF percentages, and water-holding capacity (WHC) were also determined. On-Test Leptin concentrations were not different (P > 0.10) between swine breeds; however, Off-Test Leptin concentrations did differ (P < 0.001) across genotype. Berkshire had the greatest Off-Test Leptin concentrations (6.58 +/- 0.43 ng/mL), and Duroc and Yorkshire had the lowest (3.49 and 3.96 +/- 0.68 ng/mL; respectively). In addition, Off-Test Leptin concentrations were correlated with average daily gain (r = 0.29; P < 0.001), last-rib fat thickness (r = 0.48; P < 0.001), 10th rib backfat (r = 0.52; P < 0.001), LMA (r = -0.33; P < 0.001), percent fat-free carcass lean (r = -0.51; P < 0.001), and WHC (r = 0.15; P < 0.05). Off-Test Leptin concentrations also differed by gender, with barrows having greater (P < 0.001) serum concentrations of leptin than gilts (6.55 +/- 0.48 vs 3.35 +/- 0.44). Differences exist between breeds of pigs in a manner consistent with breed-specific traits for growth, leanness, and quality; thus, leptin may serve as a useful marker for selection or identification of specific growth and carcass traits.     

Impact of ovariohysterectomy and food intake on body composition, physical activity, and adipose gene expression in cats

The mechanisms contributing to BW gain following ovariohysterectomy in domestic cats are poorly understood. Moreover, the effects of food restriction to maintain BW following spaying have been poorly studied. Thus, our primary objective was to determine the effects of spaying and food restriction to maintain BW on adipose and skeletal muscle mRNA abundance and activity levels in cats. After a 4-wk baseline period (wk 0), 8 adult (approximately 1.5 yr old) domestic shorthair cats were spayed and fed to maintain BW for 12 wk. After 12 wk, cats were fed ad libitum for an additional 12 wk. Body composition was determined, activity levels were measured, and adipose and muscle biopsies were collected at wk 0, 12, and 24. Fasting blood samples were collected at wk 0, 6, 12, 18, and 24. To maintain BW post-spay, food intake was decreased (P < 0.05) by 30%. During this phase, mRNA abundance of adipose tissue lipoprotein lipase and leptin was decreased (P < 0.05), representing only 52 and 23% of baseline expression, respectively. Interleukin-6 mRNA, however, was increased (P < 0.05) 2-fold. Physical activity was decreased (P < 0.05) by wk 12, most dramatically during the dark period (approximately 20% of baseline activity). During ad libitum feeding (wk 12 to 24), food intake, BW, body fat percentage, and total fat mass were greatly increased (P < 0.05). Compared with wk 0, circulating leptin concentrations tended to increase (P < 0.10) by wk 18 and 24 (4.45 vs. 10.02 and 9.14 ng/mL, respectively), whereas glucose (91 vs. 162 mg/dL) and triacylglyceride (30 vs. 48 mg/dL) concentrations were increased (P < 0.05) by wk 24. Adipose tissue lipoprotein lipase, hormone sensitive lipase, and adiponectin mRNA were decreased (P < 0.05) at wk 24. Adipose interleukin-6 mRNA was increased (P < 0.05) at 24 wk. Physical activity was further decreased (P < 0.05) by wk 24, during the light (60% of baseline) and dark (33% of baseline) periods. In summary, spaying and food restriction affect physical activity levels and several genes associated with lipid metabolism (decreased lipoprotein lipase), food intake (decreased leptin expression), and insulin insensitivity (increased interleukin-6). By identifying these changes, targets for nutritional intervention or lifestyle management have been identified that may curb the risk of obesity and related disorders in spayed cats.     

Development and validation of an enzyme-linked immunosorbent assay for feline trypsin-like immunoreactivity

OBJECTIVE: To develop and validate an ELISA for quantitative analysis of feline trypsin-like immunore-activity (fTLI). SAMPLE POPULATION: Purified feline cationic trypsin (fCT) and rabbit anti-fCT antiserum; blood samples from 63 healthy cats. PROCEDURES: A sandwich capture ELISA was developed, using anti-fCT antiserum purified by affinity chromatography that underwent biotinylation. Purified fCT was used for standards. The assay was validated by determination of sensitivity, working range, linearity, accuracy, precision, and reproducibility. A reference range was established by assaying serum samples from the 63 healthy cats. RESULTS: Sensitivity was 1.23 microg/L; working range was 2 to 567 microg/L. Ratios of observed versus expected results for 4 samples tested at various dilutions ranged from 90.0 to 120.7%. Ratios of observed versus expected results for 5 samples spiked with various concentrations of fCT ranged from 82.0 to 101.8%. Intra- and inter-assay coefficients of variability ranged from 9.9 to 11.1% and from 10.2 to 21.7%, respectively. The reference range for serum fTLI measured with this ELISA was 12 to 82 microg/L. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that an ELISA can be used to measure serum fTLI in cats. The ELISA was sufficiently sensitive, linear, accurate, precise, and reproducible for clinical use.     

Sandwich enzyme-linked immunosorbent assay of canine leptin

Leptin is the ob gene product secreted from adipocytes in mammals, and thereby its plasma level reflects body fat content. To establish an assay method for leptin in the dog, rabbit anti-canine leptin antibody was obtained using canine recombinant leptin as an antigen. This antibody reacted to canine leptin much stronger than mouse, rat and human leptins. Sandwich enzyme-linked immunosorbent assay (ELISA) using this antibody was developed. The serum leptin levels of 13 healthy dogs were in a range from 1.4 to 5.6 ng/ml with the mean +/- SEM of 3.0 +/- 0.3 ng/ml.     

Correlation between plasma leptin concentration and body fat content in dogs

OBJECTIVE: To evaluate the relationship between plasma leptin concentration and body fat content in dogs. ANIMALS: 20 spayed female Beagles that were 10 months old at the start of the experiment. PROCEDURE: Dogs were kept under regulated feeding and exercise conditions for 21 weeks, resulting in a wide range of body weights, body condition scores (BCS), and subcutaneous thicknesses. Plasma leptin concentration was measured by use of a canine leptin-specific ELISA test to evaluate its correlation to body fat content estimated by the deuterium oxide dilution method. Plasma concentrations of glucose, cholesterol, triglycerides (TG), and nonesterified fatty acids (NEFA) were also measured. RESULTS: Body fat content (9 to 60% of body weight) was positively and closely correlated (r = 0.920; n = 20; P < 0.001) to plasma leptin concentration (0.67 to 8.06 ng/ml), compared with other variables (ie, glucose, cholesterol, TG, and NEFA; r = 0.142, 0.412, 0.074, and 0.182, respectively). CONCLUSIONS AND CLINICAL RELEVANCE: The positive relationship between plasma leptin concentration and body fat content in dogs was similar to correlations reported for humans and rodents, suggesting that plasma leptin is a quantitative marker of adiposity in dogs.     

Agarose gel serum protein electrophoresis in cats with and without lymphoma and preliminary results of tandem mass fingerprinting analysis

Background: Serum electrophoretic profiles in cats are poorly characterized with respect to the proteins that comprise the globulin fractions, and interpretation of the electrophoretograms is routinely done in the absence of information about identity of the proteins found within each fraction. Objectives: The aims of this study were to compare protein fractions separated by serum protein electrophoresis (SPE) in healthy cats and in cats with lymphoma and to confirm some component proteins in the major fractions following SPE using tandem mass fingerprinting analysis (TMFA). Methods: Total protein concentration was measured and agarose gel SPE performed on serum from 14 healthy cats and 14 cats with lymphoma. The absolute protein concentration within each fraction was compared between the 2 groups. Bands corresponding to the SPE fractions were excised from the gels of 2 control cats and 1 cat with lymphoma and analyzed by liquid chromatography coupled to mass spectrometry. Results were compared with sequences in the National Center for Biotechnology Information protein database. Results: Median albumin concentrations were significantly decreased and median β‐globulin concentrations were significantly increased in cats with lymphoma. Narrow electrophoretic spikes were present in the β/γ‐globulin fraction in 3 cats with lymphoma. Following TMFA, multiple proteins were identified in each fraction, and their mobility agreed with results from previous studies generated using alternative techniques. Inter‐α (globulin) inhibitor 4 was identified in feline serum for the first time. Conclusions: Cats with lymphoma had lower albumin and higher β‐globulin concentrations than did healthy cats. Despite limitations of one‐dimensional agarose gel SPE, TMFA provided preliminary data to confirm the protein components of the various fractions.     

Feline plasma cortisol (hydrocortisone) measured by radioimmunoassay.

Plasma cortisol (hydrocortisone) was measured by radioimmunoassay in 6 normal cats. Blood was collected from the cats by venipuncture at intervals of 3 hours for 3 days. Resting plasma cortisol concentrations averaged 17.0 +/- 2.8 (SD) ng/ml and ranged from nondetectable (less than 3 ng/ml) to 82.8 ng/ml. Of 144 plasma samples, 95% contained less than 40 ng of cortisol/ml. Circadian rhythm of cortisol secretion was not detected, suggesting that adrenal function tests may be started in feline patients at any time of day. Intramuscular injection of 2.2 U of ACTH gel/kg of body weight caused detectable increase in plasma cortisol concentrations at 1 and 2 hours after injection. Maximal response to ACTH in the 6 cats ranged from 41.6 to 178.4 ng/ml. Oral administration of 0.1 mg of dexamethasone/kg suppressed plasma cortisol to nondetectable concentrations for 32 hours in 5 of the 6 cats.     

Impairment of cellular and humoral immunity in overweight Mongolian gerbils (Meriones unguiculatus)

Animal immunity is usually impaired in obesity. We know little about the effect of being overweight or obese on the immune function of wild rodents. The present study is aimed to test the hypothesis that immunity is suppressed in overweight Mongolian gerbils (Meriones unguiculatus). In the study, 16 overweight (body mass: 90.8–127.6 g) and 16 lean gerbils (body mass: 60.5–77.7 g) were randomly selected from a total of 174 male gerbils (body mass range: 55.8–144.7 g). Half of the overweight and lean males were injected with sterile saline; the others were immunochallenged (IC) with phytohaemagglutinin and keyhole limpet hemocyanin to assess cellular and humoral immunity, respectively. Body fat mass, wet and dry spleen mass, leukocyte counts, blood glucose levels and serum leptin levels were significantly higher in the overweight gerbils than in the lean gerbils. However, phytohemagglutinin response indicative of cellular immunity and immunoglobulin G concentrations was significantly lower in the IC overweight gerbils than in the IC lean gerbils. These results indicate that cellular and humoral immunity are impaired in the overweight gerbils. Excessive body fat mass, higher leukocyte counts and serum leptin levels imply that overweight gerbils are in a low grade inflammatory state.