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Human Leptin ELISA

Instructions for UseEnglish

Catalogue No. TE1016For Research Use Only.

TECO®Leptin

TE10

16_0

2e|1

1/20

08©TECO

med

ical

Group

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Technical Services:

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Or contact our local representative in your country.

TECOmedical AGHeadquarters TECOmedical Group

Gewerbestrasse 104450 SissachSwitzerland

phone +41(0)61 985 81 00fax +41(0)61 985 81 09

mail [email protected] www.tecomedical.com

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Tests

Kit Instructions

LOT

Lot Number

Exp

Expiry Date

Caution: irritant

REF

TE 1014

8°C

46°F

2°C

36°F

Storage Temperature Manufacturer Caution: read instructions

TECO® Human Leptin ELISA Kit

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1 plateAntibody Coated Wells12 break apart strips of 8 wells (12 x 8 in total),in a frame, Ready to use

1 x 0.75 ml

1 x 0.75 mlStandard B10 ng/ml - lyophilized

1 x 0.75 mlStandard C25 ng/ml - lyophilized

1 x 0.75 mlStandard D50 ng/ml - lyophilized

1 x 0.75 mlStandard E100 ng/ml - lyophilized

1 x 0.5 mlControl 1lyophilized, Range as indicated on data sheet

1 x 0.5 mlControl 2lyophilized, Range as indicated on data sheet

1 x 25 mlDilution BufferReady for use

1 x 12 mlAntibody-HRP-ConjugateReady for use

1 x 12 mlTMB SubstrateReady for use

1 x 50 mlWash Buffer20 times concentrated

1 x 12 mlStop Solution – 0.2 M H2S040.2 M sulfuric acid, ready for use

2 piecesCover for Microtiterplate, adhesive

1 xKit instruction

Symbol Description Format

Reagents and Materials Supplied:

Standard A1 ng/ml - lyophilized

StorageStore kit at 2–8 °C. Do not freeze. Store unused reagents at 2–8 °C.

Instructions for UseThe TECO® Human Leptin kit is a sensitive ”two-site” sandwich enzyme linked immunosorbentin-vitro assay for the quantitative determination of leptin in human plasma and serum.

BackgroundLeptin, the product of the ob gene [1, 2], is a recently discovered (1994) single-chain proteo-hormone with a molecular weight of 16 kD, which is thought to play a key role in the regulationof body weight. Its amino acid sequence exhibits no major homologies with other proteins [1].Leptin is almost exclusively produced by differentiated adipocytes [3–5]. It acts on the centralnervous system, in particular the hypothalamus, thereby suppressing food intake and stimula-ting energy expenditure [2, 6–9]. Leptin receptors – alternatively spliced forms exist that differin length – belong to the cytokine class I receptor family [10–12]. They are found ubiquitously inthe body [10, 11, 13, 14] indicating a general role of leptin, which is currently not fully under-stood.

A circulating form of the leptin receptor exists which acts as one of several leptin bindingproteins [15]. Besides its metabolic effects, leptin was shown to have a strong influence on anumber of endocrine axes. In male mice, it blunted the starvation-induced marked decline of LH,testosterone, thyroxine and the increase of ACTH and corticosterone. In female mice, leptinprevented the starvation-induced delay in ovulation [16]. Ob/ob mice, which are leptin deficientdue to an ob gene mutation, are infertile. This defect could be corrected by administration ofleptin, but not through weight loss due to fasting [17], suggesting that leptin is pivotal forreproductive functions.

All these actions may, at least in part, be explained by the suppressive effect of leptin onneuropeptide Y (NPY) expression and secretion by neurons in the arcuate nucleus [6, 18, 19].NPY is a strong stimulator of appetite [20, 21] and is known to be involved in the regulation ofvarious pituitary hormones, e.g. suppression of GH through stimulation of somatostatin [22, 23],suppression of gonadotropins [23] or stimulation of the pituitary-adrenal axis [21].

The most important variable that determines circulating leptin levels is body fat mass [24 – 26].Obviously, under conditions of regular eating cycles, leptin reflects the proportion of adiposetissue [27] showing an exponential relationship [37]. This constitutive synthesis of leptin ismodulated by a number of non-hormonal and hormonal variables. Stimulators in both rodentsand humans are overfeeding [28, 29], insulin [3, 5, 30 – 33] and glucocorticoids [5, 34 – 36].Suppression has been shown for fasting [27], cAMP and beta-3-adrenoceptor agonists [35].From these findings it becomes clear that leptin is an integral component of various metabolicand endocrine feedback loops [38].

It is important to note that serum leptin levels show a moderate circadian variation with a peakduring the night at about 2 a.m. [37]. The leptin values at this time are about 30 to 100 % higherthan the levels measured in the morning or early afternoon. This variation together with theinfluence of food intake needs to be taken into account, when blood samples are collected.

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Under fairly standardized conditions, i.e. normal eating cycles and blood sampling in themorning or early afternoon, a single leptin measurement is informative.

Leptin levels are high in most obese individuals suggesting the presence of leptin insensitivity[20, 26, 37, 38, 41, 42]. In a small percentage of patients, however, leptin levels have been foundinappropriately low with respect to their fat mass. It remains for future studies to prove thatthese individuals represent a new pathophysiologic entity: leptin deficiency. Since leptin hasalso been shown to be of great importance for reproductive functions, possible new pathophy-siologic mechanisms may be discovered relating infertility to insufficient leptin production.

The discovery of leptin has released an avalanche of research activities seeking to understand theregulation and actions of this new hormone. Most importantly, it has provided a key to betterunderstand the physiology of body weight regulation and to unveil possible pathophysiologicmechanisms in both obesity and nutritional disorders. Further, it may provide new insights intocertain causes of infertility.

The widespread importance makes leptin an interesting parameter for researchers investigatingmetabolic syndrome, obesity, cachexia and other metabolic disturbances related to indivi-duals with nutritional disorders.

This enzyme immunoassay kit is suited for measuring human leptin in serum or plasma, andconditioned adipocyte culture media for scientific research purposes.

6

References

[1] Zhang Y, Proenca R, Maffei M, BaroneM, Leopold L, Friedman JM.Positional cloning of the mouseobese gene and its human homologue.Nature. 1994; 372:425-432.

[2] Halaas JL, Gajiwala KS, Maffei M, et al.Weight-reducing effects of the plasmaprotein encoded by the obese gene.Science. 1995; 269:543-546.

[3] MacDougald OA, Hwang CS, Fan H,Lane MD.Regulated expression of the obesegene product (leptin) in white adiposetissue and 3T3-L1 adipocytes.Proc Natl Acad Sci U S A. 1995;92:9034-9037.

[4] Rentsch J, Chiesi M.Regulation of ob gene mRNA levels incultured adipocytes.FEBS Lett. 1996; 379:55-59.

[5] Wabitsch M, Jensen PB, Blum WF, et al.Insulin and cortisol promote leptinproduction in cultured human fatcells.Diabetes. 1996; 45:1435-1438.

[6] Stephens TW, Basinski M, Bristow PK,et al.The role of neuropeptide Y in theantiobesity action of the obese geneproduct.Nature. 1995; 377:530-532.

[7] Campfield LA, Smith FJ, Guisez Y, DevosR, Burn P.Recombinant mouse OB protein:evidence for a peripheral signallinking adiposity and central neuralnetworks.Science. 1995; 269:546-549.

[8] Pelleymounter MA, Cullen MJ, BakerMB, et al.Effects of the obese gene product onbody weight regulation in ob/ob mice.Science. 1995; 269:540-543.

[9] Levin N, Nelson C, Gurney A, Vandlen R,de-Sauvage F.Decreased food intake does notcompletely account for adiposityreduction after ob protein infusion.Proc Natl Acad Sci U S A. 1996;93:1726-1730.

[10] Tartaglia LA, Dembski M, Weng X, et al.Identification and expression cloningof a leptin receptor, OB-R.Cell. 1995; 83:1263-1271.

[11] Chen H, Charlat O, Tartaglia LA, et al.Evidence that the diabetes geneencodes the leptin receptor:identification of a mutation in theleptin receptor gene in db/db mice.Cell. 1996; 84:491-495.

[12] Lee GH, Proenca R, Montez JM, et al.Abnormal splicing of the leptinreceptor in diabetic mice.Nature. 1996; 379:632-635.

[13] Lynn RB, Cao GY, Considine RV,Hyde TM, Caro JF.Autoradiographic localization ofleptin binding in the choroid plexusof ob/ob and db/db mice.Biochem Biophys Res Commun. 1996;219:884-889.

7

References

[14] Considine RV, Considine EL, Williams CJ,Hyde TM, Caro JF.The hypothalamic leptin receptor inhumans: identification of incidentalsequence polymorphisms andabsence of the db/db mouse andfa/fa rat mutations.Diabetes. 1996; 45:992-994.

[15] Sinha MK, Opentanova I, Ohannesian JP,et al.Evidence of free and bound leptin inhuman circulation.J Clin Invest. 1996; 98:1277-1282.

[16] Ahima RS, Prabakaran D, Mantzoros C,et al.Role of leptin in the neuroendocrineresponse to fasting.Nature. 1996; 382:250-252.

[17] Chehab FF, Lim ME, Lu R.Correction of the sterility defect inhomozygous obese female mice bytreatment with the humanrecombinant leptin.Nat Genet. 1996; 12:318-320.

[18] Schwartz MW, Baskin DG, Bukowski TR,et al.Specificity of leptin action onelevated blood glucose levels andhypothalamic neuropeptide Y geneexpression in ob/ob mice.Diabetes. 1996; 45:531-535.

[19] Schwartz MW, Seeley RJ, Campfield LA,Burn P, Baskin DG.Identification of targets of leptinaction in rat hypothalamus.J Clin Invest. 1996; 98:1101-1106.

[20] Campfield LA, Smith FJ, Burn P.The OB protein (leptin) pathway – alink between adipose tissue massand central neural networks.Horm Metab Res. 1996; 28:619-632.

[21] Rohner-Jeanrenaud F, Cusin I, SainsburyA, Zakrzewska KE, Jeanrenaud B.The loop system betweenneuropeptide Y and leptin in normaland obese rodents.Horm Metab Res. 1996; 28:642-648.

[22] Chan YY, Steiner RA, Clifton DK.Regulation of hypothalamicneuropeptide-Y neurons by growthhormone in the rat.Endocrinol. 1996; 137:1319-1325.

[23] Pierroz DD, Catzeflis C, Aebi AC,Rivier JE, Aubert ML.Chronic administration of neuro-peptide Y into the lateral ventricleinhibits both the pituitary-testicularaxis and growth hormone and insulin-like growth factor I secretion in intactadult male rats.Endocrinol. 1996: 137:3-12.

[24] Frederich RC, Hamann A, Anderson S,Lollmann B, Lowell BB, Flier JS.Leptin levels reflect body lipidcontent in mice: evidence for diet-induced resistance to leptin action.Nat Med. 1996; 1:1311-1314.

[25] Maffei M, Halaas J, Ravussin E, et al.Leptin levels in human and rodent:measurement of plasma leptin and obRNA in obese and weight-reducedsubjects.Nat Med. 1995; 1:1155-1161.

8

References

[26] Considine RV, Sinha MK, Heiman ML,et al.Serum immunoreactive-leptinconcentrations in normal-weight andobese humans.N Engl J Med. 1996: 334:292-295.

[27] Kolaczynski JW, Considine RV,Ohannesian J, et al.Responses of leptin to short-termfasting and refeeding in humans:A link with keto-genesis but notketones themselves.Diabetes. 1996; 45:1511-1515.

[28] Harris RB, Ramsay TG, Smith SR,Bruch RC.Early and late stimulation of obmRNA expression in meal-fed andoverfed rats.J Clin Invest. 1996; 97:2020-2026.

[29] Kolaczynski JW, Ohannesian J,Considine RV, Marco C, Caro JF.Response of leptin to short-term andprolonged overfeeding in humans.J Clin Endocrinol Metab. 1996;91:4162-4165.

[30] Saladin R, De-Vos P, Guerre-Millo M,et al.Transient increase in obese geneexpression after food intake or insulinadministration.Nature. 1995; 377:527-529.

[31] Cusin I, Sainsbury A, Doyle P,Rohner-Jeanrenaud F, Jeanrenaud B.The ob gene and insulin.A relationship leading to clues to theunderstanding of obesity.Diabetes. 1995; 44:1467-1470.

[32] Kolaczynski JW, Nyce MR,Considine RV, et al.Acute and chronic effects of insulinon leptin production in humans:studies in vivo and in vitro.Diabetes. 1996; 45:699-701.

[33] Malström R, Taskinen M-R,Karonen S-L, Yki-Järvinen H.Insulin increases plasma leptinconcentrations in normal subjectsand patients with NIDDM.Diabetologia. 1996; 39:993-996.

[34] De-Vos P, Saladin R, Auwerx J, Staels B.Induction of ob gene expression bycorticosteroids is accompanied bybody weight loss and reduced foodintake.J Biol Chem. 1995; 270:15958-15961.

[35] Slieker LJ, Sloop KW, Surface PL, et al.Regulation of expression of ob mRNAand protein by glucocorticoids andcAMP.J Biol Chem. 1996; 271:5301-5304.

[36] Miell JP, Englaro P, Blum WF.Dexamethasone induces an acuteand sustained rise in circulatingleptin levels in normal humansubjects.Horm Metab Res. 1996; 28:704-707.

[37] Sinha MK, Ohannesian JP, Heiman ML,et al.Nocturnal rise of leptin in lean, obese,and non-insulin- dependent diabetesmellitus subjects.J Clin Invest. 1996; 97:1344-1347.

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References

[38] Havel PJ, Kasim-Karakas S, Dubuc GR,Mueller W, Phinney SD.Gender difference in plasma leptinconcentrations.Nature Med. 1996; 2:949-950.

[39] Rosenbaum M, Nicolson M, Hirsch J,et al.Effects of gender, body composition,and menopause on plasmaconcentrations of leptin.J Clin Endocrinol Metab. 1996; 81:3424-3427.

[40] Hassink SG, Sheslow DV, de Lancey E,Opentanova I, Considine RV, Caro JF.Serum leptin in children with obesity:relationship to gender anddevelopment.Pediatrics. 1996: 98:201-203.

[41] Scholz GH, Englaro P, Thiele I, et al.Dissociation of serum leptinconcentration and body fat contentduring long term dietary interventionin obese individuals.Horm Metab Res. 1996; 28:718-723.

[42] Caro JF, Kolaczynski JW, Nyce MR,et al.Decreased cerebrospinal-fluid/serumleptin ratio in obesity: a possiblemechanism for leptin resistance.Lancet. 1996; 348:159-161.

[43] Robinson CJ, Gaines-Das R,Woollacott D, et al.The first international standard forhuman leptin and the first internationalstandard for mouse leptin:comparison of candidatepreparations by in vitro bioassaysand immunoassays.J Molecular Endocrinol. 2001; 27: 69-76.

[44] Adresse NIBSC:Blanche Lane, South Mimms,Potters Bar, Hertfordshire EN6 3QG,Great Britain.

[45] Blum WF, Juul A;Reference ranges of serum leptin.In: Leptin – the voice of adipose tissue,Blum WF et al, eds., Johann AmbrosiusVerlag, Heidelberg, 1997,s.318-326.

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Assay Principle

The TECO® assay kit for human Leptin is a Sandwich-Assay using two specific and high affinitymonoclonal antibodies. The Leptin in the samples binds to the first antibody coated on the mi-crotiter plate. In the following step the second anti-Leptin-Antibody binds in turn to the immo-bilised Leptin. The second antibody is biotinylated and will be incubated in a mixture with aStreptavidin-Peroxidase-Enzyme Conjugate. In the closing substrate reaction the turn of thecolor will be catalyzed quantitatively depending on the Leptin-level of the samples.

Materials Required and not Supplied

• Pipettes capable of dispensing 20 µl, 100 µl, 350 µl, 500 µl and 750 µl• Graduated cylinders for reconstituting or diluting reagents• Manual Aspiration System and multi-channel pipette or automatic washer for ELISA plates• Distilled water• Vortex mixer• ELISA plate reader suitable for 96 well formats and capable of measuring at 450 nm

(Reference: 590–650 nm).• ELISA Plate Shaker (≥350 rpm) (orbital shaker)• Software package for data generation and analysis

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Warnings and Precautions

This kit is intended for in vitro research use by professional persons only.Follow the instructions carefully.Observe expiration dates stated on the labels and the specified stability for reconstitutedreagents. Refer to ”Materials Safety Data Sheet” for more detailed safety information.

Material of human origin used in the preparation of this kit has been tested and found nonreactive for HIV-1 and HIV-2 as well as for HCV antibodies and HbsAg but should, nonetheless,be handled as potentially infectious.

TECOmedical AG is not liable for loss or harm caused by non-observance of the Kit instructions.

1. For Research Use Only. Not for use in diagnostic procedures.2. Treat all specimen samples as potentially biohazardous material. Follow General Precautions

when handling contents of this kit and any patient samples.3. Disposal of containers and unused contents should be done in accordance with federal and

local regulatory requirements.4. Use the supplied reagents as an integral unit prior to the expiration date indicated on the

package label.5. Store assay reagents as indicated.6. Do not use coated strips if pouch is punctured.7. Test each sample in duplicate.8. Use of multichannel pipettes or repeat pipettors is recommended to ensure the timely

delivery of liquids.9. a) 0.2 M sulfuric acid is caustic and can cause severe burns.

b) handle TMB with care.Do not ingest. Avoid contact with skin, eyes, or clothing. If contact is made, wash withwater. If ingested, call a physician.

10. As preservative is used (0.01 %) 2-Methyl-4-isothiazolin-3-one solution and (0.01 %)5-chloro-2-methyl 2H isothiazol-3-one / 2-methyl-2H-isothiazol-3-one solution for the anti-body, dilution buffer and washing buffer.Do not ingest. Avoid contact with skin, eyes, or clothing. If contact is made, wash withwater. If ingested, call a physician.

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Preparation of Reagents

Microtiterplate coated with an anti-human Leptin Antibody12 break apart strips of 8 wells (96 in total) in a frame and sealed in a foil bag. Fit strip wellsfirmly into the frame. After opening, immediately return any unused wells to the original foilpackage and seal. Store at 2–8 °C until expiration date.

Standards5 vials of lyophilized Standard containing recombinant Leptin (1, 10, 25, 50 and 100 ng/ml).Reconstitute each Standard with 750 µl of Dilution Buffer. Keep reconstituted reagents atroom temperature for 15 minutes and then mix them gently (no foam!) with a Vortex. Afterreconstitution, the Standards are stable 2 months at -20 °C. Only 3 freeze/thaw cycle orkeep in aliquotes. Store lyophilized at 2–8 °C until expiration date.

thru

Control 11 vial of lyophilized control (human serum). Reconstitute with 500 µl of Dilution Buffer.Keep reconstituted reagents at room temperature for 15 minutes and then mix them gently(no foam!) with a Vortex. After reconstitution, the control serum is stable 2 months at-20 °C (3 freeze/thaw cycles or store in aliquotes). For the exact value, refer to data sheet.Store lyophilized at 2–8 °C until expiration date.

Control 21 vial of lyophilized control (human serum). Reconstitute with 500 µl of Dilution Buffer.Keep reconstituted reagents at room temperature for 15 minutes and then mix them gently(no foam!) with a Vortex. After reconstitution, the control serum is stable 2 months at-20 °C (3 freeze/thaw cycles or store in aliquotes). For the exact value, refer to data sheet.Store lyophilized at 2–8 °C until expiration date.

Antibody-HRP Conjugate1 vial of 12 ml, ready for use. Anti-human leptin conjugated to horseradish peroxidase(HRPO). Store at 2–8 °C until expiration date.

TMB Substrate1 vial of 12 ml stabilized H2O2 Tetramethylbenzidine. Ready for use.Store at 2–8 °C until expiration date.

Wash Buffer1 vial of 50 ml of buffer. Possible precipitation in the Buffer, resolve before using by mixingand/or warming Bring the vial content to 1000 ml with distilled water. The diluted washingsolution is stable for 4 weeks at 2–8 °C. Store undiluted at 2–8 °C until expiration date.

Dilution Buffer1 vial of 25 ml, ready for use. Possible precipitation in the Buffer, resolve before using bymixing and/or warming. Store at 2–8 °C until expiration date.

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Preparation and Stability of Serum Samples

Sample TypeSerum and plasma samples are suitable (significant deviation of hLeptin levels incorresponding Serum, Heparin or EDTA Plasma samples were not found), as well as cell culture,urine and saliva.

Stability• Maximum 2 days at room temperature• Maximum 2 years at -20 °C• Maximum 5 freeze/thaw cycles

NoteMost of the time the use of undiluted samples, 20 µl per well, should be appropriate. It can beexpected that patients with a BMI >30 will have Leptin levels over 100 ng/ml: the sample shouldthen be diluted in the Dilution Buffer, e.g. 1:2.The hLeptin concentrations may be completely different in body fluids of human origin other thanserum or cell culture supernatants.

Cover for Microtiterplate2 pieces, adhesive.

Stop Solution – 0.2 M H2SO41 vial of 12 ml 0.2 M H2SO4. Ready for use. Store at 2–8 °C until expiration date.

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Assay Procedure

All determinations (Standards, Control Sera and Samples) should be assayed in duplicate. Whenperforming the assay, the Standards, Control Sera and the Samples should be pipetted as fastas possible (<15 minutes).To avoid distortions due to differences in incubation times, HRP Conjugate, Substrate Solutionand Stop Solution should be added to the plate in the same order and with the same timeinterval as the samples.

Allow all reagents to equilibrate at room temperature (20–25 °C) for at least 30 minutes.

1. Prepare the frame and the required number of coated strips .

2. Allocate the wells of the Microtiter plate for Standards, Controls and Samples.

3. Pipette 100 µl Dilution Buffer into all wells.

4. Add 20 µl Dilution Buffer in duplicate (Blank).

5. Pipette 20 µl of each Standard ( thru ), Control sera ( and ) and samples into thecorresponding wells.

6. Cover the wells with sealing tape and incubate the plate for 1 hour at room temperatureon a plate shaker (≥350 rpm).

7. After incubation, aspirate the wells by using a plate washer or manually decant by invertingthe plate. Wash the wells 3 x with 350 µl diluted washing buffer (15 seconds incubation percycle). After the last wash cycle tap the inverted wells gently on a dry absorbent surface toremove excess wash solution.

8. Pipette 100 µl of the Antibody HRP Conjugate in each well.

9. Cover the wells with sealing tape and incubate the plate for 30 minutes at room temperatureon a plate shaker (≥350 rpm).

10. After incubation wash the wells 3 x with Washing Buffer as described in step 7.

11. Pipette 100 µl of the TMB Substrate Solution in each well.

12. Incubate the plate for 15 minutes, in the dark, at room temperature (20–25 °C).

13. Add 100 µl of Stop Solution in each well.

14. Measure the colour reaction within 30 minutes at 450 nm (reference filter between590–650 nm). With strong colour reaction e. g. >3 OD, also measure at 405 nm.

Protocols for the different automatic ELISA systems are available.

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Result Analysis

For the evaluation of the assay, the absorbance values of the blank should be below 0.25 andthe absorbance values of Standard E should exceed 1.0. Samples, having higher absorbancevalues than Standard E, should be tested again with a higher dilution. A standard curve can beestablished by plotting Standard concentration on the x-axis (linear scale) against the absor-bance of the Standards on the y-axis (linear scale). The Leptin concentrations in samples canthen be read off the standard curve. A 4-parameter curve fit should be used for automatic datareduction.

Typical Results(Example only, not for use in calculation of actual results)

For each assay, the results of the controlsmust be within the target range indicated forevery lot.The QC protocol with target rangesis provided with the kit. If control values arenot within the limits of the target range, theassay results should be considered questio-nable and the samples should be tested again.

StandardsAbsorptionat 450 nm

ng/ml

A 0.083 1

B 0.680 10

C 1.449 25

D 2.165 50

E 2.763 100

L-Control 1 0.875 13.21

H-Control 2 1.551 28.00

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Observed Values

Serum leptin levels are mainly determined by body fat mass with low levels in lean individualsand high levels in obese subjects. In addition, there is a clear gender difference with higherlevels in females at a given percentage body fat. Further, leptin levels are influenced bypubertal development. Any attempt, therefore, to give ranges of expected leptin levels mustaccount for these relationships.Various methods for the estimation of body fat are available such as calculation of body massindex [weight (kg) divided by the square of height (m)] (BMI), bioelectric impedance assessment(BIA) or total body dual energy x-ray absorptiometry (DXA). Although the accuracy of BMI withrespect to reflecting true fat mass is inferior to other more sophisticated methods such as BIAor DXA, BMI provides a number of advantages:

• It is independent of the regression models applied.• It is easy to determine, only weight and height measurements are required.• It is retrospectively mostly available.• It is the most precise measure during short-term changes of fat mass, e.g. during fasting.

Therefore, the following expectation ranges of serum leptin levels were referred to BMI as themajor confounding independent variable and were stratified according to gender and pubertaldevelopment (45; see figures 1–8 and tables 1–9). After the age of 20 years, no significant agedependence was observed. These gender and age adjusted expectation ranges may be usedto compare a measured leptin level at a given BMI with normal subjects to detect deviations.The best-fit regression lines for the various subgroups are exponential curves of the form:

Leptin = a · e (b · BMI)

The 5th and 95th percentiles are given by the following equations:

Leptin = a · e (b · BMI – c)

and Leptin = a · e (b · BMI + c) respectively.

In a semi-logarithmic plot (y-axis = log leptin), these curves give straight lines. The values for a,b and c are given in table 1 according to gender and pubertal stage and also for adults. Usingthese values, the expectation ranges of leptin levels can be easily extended to lower or higherBMI ranges if required.

ExampleThe 50th percentile for boys at Tanner stages 3 and 4 is given by the following curve:

Leptin = 0.0181 · e (0.2067 · BMI)

The 5th percentile is given by: Leptin = 0.0181 · e (0.2067 · BMI 1.1919)

and the 95th percentile is given by: Leptin = 0.0181 · e (0.2067 · BMI + 1.1919)

In a semi-logarithmic plot, these lines are parallel with an equal distance to the 50th percentile.

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Calculation of standard deviation scores (SDS; Z-scores)A convenient method to detect any deviation of a measured leptin level from the correspondingobserved range is to calculate its standard deviation score by relating the leptin level atthe patient’s BMI to the average leptin value of the corresponding sex and age group andexpressing its deviation by the x-fold standard deviation. This method may be considered asnormalization to the normal reference cohort. Thus, the leptin values can be adjusted for BMI,gender and pubertal stage/age (i.e., the influence of gender, age and BMI are removed) andmay be pooled for further analysis.

Accounting for the logarithmic distribution of leptin levels, the leptin SDS can be calculated bythe following equation:

Leptin SDS = (ln(leptin) – ln(a) – b · BMI)d

In this equation, ln represents the natural logarithm (referring to the basis e). The constantsa, b and d are given in table 1 according to gender and pubertal stage/age.

Example:A boy at Tanner stage 3, BMI = 25 kg/m2, measured leptin concentration = 5 ng/ml.

Leptin SDS = (ln(5) – ln (0.0181) – 0.2067 · 25) = 0.660.6850

Constants a, b, c and d for calculation of leptin ranges and leptin SDS based on BMI.Groups of individuals were stratified according to gender and pubertal stage/age.TS= Tanner stage, n= number of subjects, a,b,c and d = constants as defined in the text.

Table 1

Cohort n a b c dMales

TS 1&2 136 0.0146 0.2706 0.8821 0.5379

TS 3&4 50 0.0181 0.2067 1.1919 0.6850

TS 5 112 0.0316 0.1462 1.0821 0.6558

Adults 380 0.0130 0.2200 1.1053 0.6740

FemalesTS 1&2 136 0.0422 0.2499 0.7849 0.4786

TS 3&4 43 0.0543 0.2357 0.5745 0.3379

TS 5 157 0.2550 0.1508 0.7053 0.4301

Adults 587 0.3042 0.1467 0.8548 0.5212

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Percentile (µg/l)

BMI(kg/m2) 1 5 50 95 99

11 0.22 0.30 0.66 1.45 1.9912 0.28 0.39 0.85 1.86 2.5613 0.36 0.50 1.09 2.38 3.2914 0.46 0.64 1.40 3.06 4.2215 0.60 0.82 1.79 3.93 5.4216 0.76 1.05 2.30 5.04 6.9617 0.98 1.35 2.95 6.47 8.9318 1.25 1.73 3.79 8.31 11.519 1.61 2.22 4.87 10.7 14.720 2.07 2.85 6.25 13.7 18.921 2.65 3.66 8.03 17.6 24.322 3.41 4.70 10.3 22.6 31.223 4.37 6.03 13.2 29.0 40.024 5.62 7.75 17.0 37.2 51.425 7.21 9.95 21.8 47.8 65.926 9.26 12.8 28.0 61.4 84.727 11.9 16.4 35.9 78.8 109.028 15.3 21.1 46.1 101.0 140.029 19.6 27.0 59.2 130.030 15.2 34.7 76.131 32.3 44.6 97.732 41.5 57.2 125.033 53.2 73.434 68.4 94.335 87.8 121.036 113.037 145.0

Percentile (µg/l)

BMI(kg/m2) 1 5 50 95 99

11 0.08 0.12 0.29 0.69 0.9912 0.01 0.16 0.38 0.91 1.3013 0.14 0.20 0.49 1.19 1.7114 0.19 0.26 0.65 1.56 2.2415 0.24 0.35 0.85 2.04 2.9316 0.32 0.46 1.11 2.68 3.8417 0.41 0.60 1.45 3.51 5.0418 0.55 0.79 1.90 4.60 6.6019 0.72 1.03 2.50 6.03 8.6620 0.94 1.35 3.27 7.90 11.321 1.24 1.77 4.29 10.4 14.922 1.62 2.33 5.62 13.6 19.523 2.12 3.05 7.37 17.8 25.524 2.78 3.99 9.66 23.3 33.525 3.65 5.24 12.7 30.6 43.926 7.78 6.87 16.9 40.1 57.527 6.27 9.0 21.7 52.5 75.428 8.22 11.8 28.5 68.9 98.829 10.7 15.5 37.4 90.3 129.030 14.1 20.3 48.9 118.031 18.5 26.6 64.232 24.3 34.8 84.133 31.8 45.6 110.034 41.7 59.8 144.035 54.6 78.436 71.6 102.037 93.9 134.038 123.0Table 2: Girls Tanner stages 1 and 2

Figure 1: Observed ranges of human serum

levels referring to BMI: Girls Tanner stage 1 & 2

(see text for details).


levels referring to BMI: Boys Tanner stage 1 & 2


Table 3: Boys Tanner stages 1 and 2

19

Percentile (µg/l)

BMI(kg/m2) 1 5 50 95 99

11 0.32 0.41 0.73 1.29 1.6312 0.41 0.52 0.92 1.63 2.0613 0.52 0.66 1.16 2.07 2.6114 0.65 0.83 1.47 2.61 3.3115 0.83 1.05 1.87 3.31 4.1916 1.05 1.33 2.36 4.19 5.3017 1.33 1.68 2.99 5.30 6.7118 1.68 2.13 3.78 6.71 8.4919 2.13 2.69 4.79 8.5 10.820 2.69 3.41 6.06 10.7 13.621 3.41 4.31 7.67 13.61 17.222 4.32 5.46 9.71 17.2 21.823 5.46 6.91 12.3 21.8 27.624 6.91 8.75 15.6 27.6 34.925 8.75 11.1 19.7 34.9 44.226 11.1 14.0 24.9 44.2 56.027 14.0 17.7 31.6 56.0 70.928 17.8 22.5 39.9 70.9 89.729 22.5 28.4 50.5 89.7 114.030 28.4 36.0 63.9 114.0 144.031 36.0 45.6 80.9 144.032 45.6 57.7 80.2 144.033 57.7 73.0 102.034 73.0 92.4 130.035 92.4 117.036 117.0 148.037 148.0

Percentile (µg/l)

BMI(kg/m2) 1 5 50 95 99

11 0.03 0.05 0.18 0.58 0.9412 0.04 0.07 0.22 0.71 1.1613 0.49 0.08 0.27 0.88 1.4314 0.06 0.10 0.33 1.08 1.7515 0.07 0.12 0.40 1.32 2.1616 0.09 0.15 0.49 1.63 2.6517 0.11 0.18 0.61 2.00 3.2618 0.14 0.23 0.75 2.46 4.0119 0.17 0.28 0.92 3.03 4.9320 0.21 0.34 1.13 3.72 6.0621 0.26 0.42 1.39 4.58 7.4622 0.32 0.52 1.71 5.63 9.1723 0.39 0.64 2.10 6.92 11.324 0.48 0.78 2.58 8.51 13.925 0.59 0.96 3.18 10.5 17.026 0.73 1.19 3.91 12.9 21.027 0.89 1.46 4.80 15.8 25.828 1.10 1.79 5.90 19.4 31.729 1.35 2.20 7.26 23.9 39.030 1.66 2.71 8.93 29.4 48.031 2.05 3.33 11.0 36.2 58.932 2.51 4.09 13.5 44.5 72.433 3.09 5.04 16.6 54.7 89.134 3.80 6.20 20.4 67.2 109.035 4.68 7.62 25.1 82.6 134.036 5.75 9.37 30.9 101.037 7.07 11.5 37.9 124.038 8.7 14.2 46.739 10.7 17.4 57.440 13.1 21.4 70.5

Table 4: Girls Tanner stages 3 and 4


levels referring to BMI: Girls Tanner stage 3 & 4



levels referring to BMI: Boys Tanner stage 3 & 4


Table 5: Boys Tanner stages 3 and 4

Percentile (µg/l)

BMI(kg/m2) 1 5 50 95 99

11 0.50 0.66 1.34 2.71 3.6212 0.58 0.77 1.56 3.15 4.2113 0.67 0.89 1.81 3.67 4.8914 0.78 1.04 2.11 4.26 5.6915 0.91 1.21 2.45 4.96 6.6216 1.05 1.41 2.85 5.76 7.7017 1.22 1.64 3.31 6.70 8.9518 1.42 1.90 3.85 7.79 10.419 1.66 2.21 4.48 9.06 12.120 1.93 2.57 5.20 10.5 14.121 2.24 2.99 6.05 12.3 16.422 2.60 3.48 7.03 14.2 19.023 3.03 4.04 8.18 16.6 22.124 3.52 4.70 9.51 19.3 25.725 4.09 5.46 11.0 22.4 29.926 4.76 6.35 12.9 26.0 34.827 5.53 7.39 15.0 30.3 40.428 6.43 8.59 17.39 35.2 47.029 7.48 9.99 20.2 40.9 54.730 8.70 11.6 23.5 47.6 63.531 10.1 13.5 27.3 55.3 73.932 11.8 15.7 31.8 64.4 85.933 13.7 18.3 37.0 74.9 99.934 15.9 21.2 43.0 87.0 116.035 18.5 24.7 50.0 101.0 135.036 21.5 28.7 58.1 118.037 25.0 33.4 67.6 137.038 29.1 38.8 78.639 33.8 45.1 91.440 39.4 52.5 106.0

Percentile (µg/l)

BMI(kg/m2) 1 5 50 95 99

11 0.03 0.05 0.16 0.47 0.7312 0.04 0.06 0.18 0.54 0.8413 0.05 0.07 0.21 0.62 0.9714 0.05 0.08 0.24 0.72 1.1215 0.06 0.10 0.28 0.84 1.3016 0.07 0.11 0.33 0.97 1.5117 0.08 0.13 0.38 1.12 1.7418 0.1 0.15 0.44 1.3 2.0219 0.11 0.17 0.51 1.50 2.3420 0.13 0.2 0.59 1.74 2.721 0.15 0.23 0.68 2.01 3.1322 0.17 0.27 0.79 2.33 3.6223 0.20 0.31 0.91 2.69 4.1924 0.23 0.36 1.05 3.12 4.8525 0.27 0.41 1.22 3.61 5.6226 0.31 0.48 1.41 4.17 6.527 0.36 0.55 1.63 4.83 7.5228 0.41 0.64 1.89 5.59 8.7129 0.48 0.74 2.19 6.47 10.130 0.55 0.86 2.54 7.49 11.731 0.64 1.00 2.94 8.67 13.532 0.74 1.15 3.4 10.0 15.633 0.86 1.33 3.94 11.6 18.134 0.99 1.54 4.55 13.4 20.935 1.15 1.79 5.27 15.6 24.236 1.33 2.07 6.10 18.0 28.137 1.54 2.39 7.06 20.8 32.538 1.78 2.77 8.17 24.1 37.639 2.06 3.21 9.46 27.9 43.540 2.38 3.71 10.9 32.3 50.3

Table 6: Girls Tanner stages 5


levels referring to BMI: Girls Tanner stage 5



levels referring to BMI: Boys Tanner stage 5


Table 7: Boys Tanner stages 5

20

Percentile (µg/l)

BMI(kg/m2) 1 5 50 95 99

11 0.46 0.65 1.53 3.59 5.1012 0.53 0.75 1.77 4.16 5.9013 0.61 0.87 2.05 4.82 6.8314 0.71 1.01 2.37 5.58 7.9115 7.82 1.17 2.75 6.46 9.1716 0.95 1.35 3.18 7.48 10.6117 1.10 1.57 3.68 8.66 12.318 1.28 1.81 4.27 10.0 14.219 1.48 2.10 4.94 11.6 16.520 1.71 2.43 5.72 13.4 19.121 1.99 2.82 6.62 15.6 22.122 2.30 3.26 7.67 18.0 25.623 2.66 3.78 8.88 20.9 29.324 3.08 4.38 10.3 24.2 34.325 3.57 5.07 11.9 28.0 39.726 4.13 5.87 13.8 32.4 46.027 4.79 6.79 16.0 37.5 53.328 5.54 7.87 18.5 43.5 61.729 6.42 9.11 21.4 50.4 71.530 7.43 10.6 24.8 58.3 82.831 8.61 12.2 28.7 67.5 95.832 9.97 14.1 33.3 78.2 111.033 11.5 16.4 38.5 90.5 129.034 13.4 19.0 44.6 105.0 149.035 15.5 22.0 51.6 121.036 17.9 25.4 59.8 141.037 20.8 29.5 69.338 24.0 34.1 80.239 27.8 39.5 92.940 32.2 45.7 108.0


levels referring to BMI: Adult women (see text

for details).

Table 8: Adult women


levels referring to BMI: Adult men (see text for

details).

Table 9: Adult men

21

Percentile (µg/l)

BMI(kg/m2) 1 5 50 95 99

11 0.03 0.05 0.15 0.44 0.6912 0.04 0.06 0.18 0.55 0.8713 0.05 0.08 0.23 0.69 1.0814 0.06 0.09 0.28 0.85 1.3415 0.07 0.12 0.35 1.06 1.6716 0.09 0.15 0.44 1.33 2.0917 0.12 0.18 0.55 1.65 2.6018 0.14 0.23 0.68 2.06 3.2419 0.18 0.28 0.85 2.57 4.0420 0.22 0.35 1.06 3.20 5.0321 0.23 0.44 1.32 3.98 6.2722 0.35 0.54 1.64 4.97 7.8123 0.43 0.78 2.05 6.19 9.7324 0.54 0.85 2.55 7.71 12.125 0.67 1.05 3.18 9.61 15.126 0.83 1.31 3.96 12.0 18.827 1.04 1.64 4.94 14.9 23.528 1.30 2.04 6.15 18.6 29.229 1.61 2.54 7.67 23.2 36.430 2.01 3.16 9.56 28.9 45.431 2.51 3.94 11.9 36.0 56.632 3.12 4.91 14.8 44.9 70.533 3.89 6.12 18.5 55.8 87.834 4.85 7.63 23.0 69.6 109.035 6.04 9.51 28.7 86.7 136.036 7.53 11.8 35.8 108.037 9.38 14.8 44.6 135.038 11.7 18.4 55.539 14.6 22.9 69.240 18.2 28.6 86.2

Test Performance

CalibrationThe Standards from the kit are prepared from recombinant Leptin, calibrated against the WHOinternational standard NIBSC 97/594.

Precision(Inter assay)

(Intra assay)

Detection LimitThe analytical sensitivity of the assay yields 0.2 ng/ml (2 x SD of zero standards).

Recovery TestThe recovery of recombinant hLeptin in different human sera yielded on average 102 % of thetheoretical expected value.

Parallelism

Mean = Average Value, SD = Standard Deviation, CV = Variation coefficient

Sample Mean value Standard deviation CV (%)Sample 1 3.95 0.32 8.3

Sample 2 6.51 0.44 6.8

Sample 3 33.16 2.56 7.7

Sample N Mean value (ng/ml) Standard deviation (ng/ml) CV (%)Sample 1 15 4.97 0.27 5.4

Sample 2 15 37.11 2.55 6.8

Dilution Sample 1 (ng/ml) Dilution Sample 2 (ng/ml)1:1 35.2 1:1 17.8

1:2 35.0 1:2 17.3

1:5 38.6 1:5 18.0

1:10 35.5 1:10 17.7

1:20 40.6 1:20 15.9

Mean/1 SD/CV % 36.96/2.5/6.8 Mean/1 SD/CV % 17.4/0.86/4.97

22

InterferenceSerum samples have been spiked with different concentrations of possibly interfering substancesand the amount of leptin was measured and compared with the leptin concentration in the samesample without any spiking. None of the tested substances interfered significantly with leptinmeasurement.

Cross-reactivityThis assay is specific for human leptin. There is a low cross-reaction with mouse, rat, horse,sheep and chicken-leptin. No cross-reactivity was found with other proteins such as insulin orIGF-I.

RemarkThe data quoted in this instruction should be used for guidance only. It is recommended thateach laboratory includes its own panel of control samples in the assay. In order to follow GLPguidelines, each laboratory should establish its own ranges for leptin levels.

% Triglyceride 100 mg/ml Bilirubin 100 µg/ml Hemoglobin 100 µg/mlSample 1 95 101 94

Sample 2 107 105 105

Sample 3 111 101 101

23

TECO® Human Leptin

Assay Procedure – Quick Guide

Prepare the required number of Assay Strips

Pipette 100 µl Dilution Buffer in all wells

Pipette 20 µl Standards thru , Controls and and Samples

After sealing the plate, incubate 60 min at 20–25 °C on a plate shaker ≥350 rpm

Aspirate and wash 3 x with 350 µl Wash Buffer, aspirate and tap the inverted wellsgently on a clean dry absorbent surface

Add 100 µl Antibody HRP Conjugate into each well

After sealing the plate, incubate 30 min at 20–25 °C on a plate shaker ≥350 rpm

Aspirate and wash 3 x with 350 µl Wash Buffer, aspirate and tap the inverted wellsgently on a clean dry absorbent surface

Add 100 µl Stop Solution into each well

Measure the absorbance at 450 nm within 30 minutesQuantification software, 4-parameter fit:

y = (A-D)/(1+(x/C)^B)+DReference measurement should be performed at 590-650 nm

• Bring samples and reagents to room temperature. Mix the samples well.

• Standards thru : Reconstitute each vial with 750 µl Dilution Buffer .

• Controls and : Reconstitute each vial with 500 µl Dilution Buffer .

• Washing Buffer : Dilute 1:20 with Distilled water.

Please read Kit instruction before using the Quick Guide.

Add 100 µl TMB Substrate into each well

Incubate 15 min at 20–25 °C in the dark

Add 20 µl Dilution Buffer into wells (Blank)

teco leptin - quidel · pdf filecatalogue no. te1016 for research use only. teco ®leptin...

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