Journal Club

1. Journal Club Anderwald C, Gastaldelli A, Tura A, Krebs M, Promintzer-Schifferl M, Kautzky-Willer A, Stadler M, Defronzo RA, Pacini G, Bischof MG. Mechanism and Effects of Glucose Absorption during an Oral Glucose Tolerance Test Among Females and Males. J ClinEndocrinolMetab. 2010 Dec 8. [Epub ahead of print] Feero WG, Guttmacher AE, McCarthy MI. Genomics, Type 2 Diabetes, and Obesity. [Review Article] N Engl J Med. 2010 Dec 9;363(24):2339-2350. 埼玉医科大学　総合医療センター　内分泌・糖尿病内科 Department of Endocrinology and Diabetes, Saitama Medical Center, Saitama Medical University 松田　昌文 Matsuda, Masafumi 2010年12月16日8:30-8:55 ８階　医局

2. インスリン注入 アルゴリズム 筋肉 内因性インスリン分泌は無視できるレベルとなる インスリンクランプ法 グルコースクランプ法の一つ 糖注入量 糖注入量 インスリン (動脈側） 　　　　　　 （一定にするように注入) 血糖 (動脈側) (mg/kg per min) (mg/kg per min) (mg/dl) ( U/ml) 凸 ( U/ml) m 凸 m 100 100 250 250 80 80 200 10.0 200 10.0 60 150 60 150 7.5 7.5 40 40 100 100 5.0 5.0 20 20 50 2.5 50 2.5 0 0 0 0 0 0 0 40 80 120 0 40 80 120 0 40 80 120 0 40 80 120 分 分

4. BACKGROUND Several epidemiological studies revealed sex-specific differences during oral glucose tolerance tests (OGTTs), such as higher prevalence of glucose intolerance (i.e. increased glucose at the end of the OGTT) in females, which was not yet explained. Thus, we aimed to analyze sex related distinctions on OGTT glucose metabolism, including gut absorption, in healthy humans.

5. METHODS Females (n=48) and males (n=26) with comparable age (females, 45±1 yr; males, 44±2 yr) and body mass index (both, 25 ±1 kg/m2) but different height (females, 166 ±1 cm; males, 180±2 cm; P<0.000001), all normally glucose tolerant, as tested by frequently sampled, 3-h (75-g) OGTTs, underwent hyperinsulinemic [40 mU/(min ・ m2)] isoglycemic clamp tests with simultaneous measurement of endogenous glucose (D-[6,6-2H2]glucose) production (EGP). EGP and glucose disappearance during OGTT were calculated from logarithmic relationships with clamp test insulin concentrations. After reliable model validation by double-tracer technique (r = 0.732; P <0.007), we calculated and modeled gut glucose absorption (ABS). Females were examined in the first phase of their menstrual cycle (i.e. 5–12 d after the period) if they were not postmenopausal.

6. A primed continuous infusion [from 120 to 115 min at 4 mg/(min kg) fat-free mass (obtained from Tanita measure) and from115 to 15 min at 0.04 mg/(min ・kg) fat-free mass] of D-[6,6-2H2]glucose (98% enriched; Cambridge Isotope Laboratories, Andover, MA) was given in 44 participants (59% of the study population: 29 females and 15 males) before and until 15 min after the start of the clamp test to determine fasting EGP EGP ＝glucose infusion rate (GIR)mean× [(enrichment inf/enrichmentplasma) －1], where GIRmean is the mean GIR during the preceding 30 min, enrichmentinf is the MPE of glucose in infusate, and enrichmentplasma is the MPE of plasma glucose during steady-state conditions of the clamp

7. the increase of circulating glucose (d gluccirc)overtime (dt) is the result of gain from gut glucose absorption (ABS) and EGP and loss because of glucose uptake (Rd) dgluccirc/dt＝1/VG×[BW×(EGP－Rd)＋ABS](equation 1), with initial conditions of gluc (0) fasting glucose concentration; ABS (0)=0, and Rd (0)=EGP (0). BW is the body weight, and Vg is the oral glucose distribution volume, previously estimated as approximately 9% of body weight EGP in females ＝1.889 －0.342 ×ln[insulin (microunits per milliliter)] (equation 2) EGP inmales ＝2.542 －0.496 ×ln[insulin (microunits per milliliter)] (equation 3) Rd in females＝－3.96±0.46＋2.86±0.18 ×ln[insulin (microunits per milliliter)] (equation 4) Rd in males＝－3.76±0.53＋2.86 ±0.25 ×ln[insulin (microunits per milliliter)] (equation 5).

9. FIG. 1. A, Schematic model of glucose fate and effects during an OGTT, with stimulating (＋) and inhibiting (－) actions, as indicated; B, logarithmic relationship between plasma insulin concentrations over the broad range between fasting and supraphysiologicalinsulinemia and Rd and EGP (inset) in nondiabetic humans (n ＝6, □) during three-stepped (1, 2, and 4 mUinsulin/min・kg) hyperinsulinemic clamp tests [other information published elsewhere (9)]; C and D, logarithmic relationship of plasma insulin concentrations with EGP in females (○, n ＝29) and males (●, n ＝15) (C), and Rd in females (○, n ＝48) and males (●, n ＝26) (D), both measured during one stepped [40 mU insulin/(min・m2)] hyperinsulinemic clamp test;

10. FIG. 1. C and D, logarithmic relationship of plasma insulin concentrations with EGP in females (○, n ＝29) and males (●, n ＝15) (C), and Rd in females (○, n ＝48) and males (●, n ＝26) (D), both measured during one stepped [40 mU insulin/(min ・m2)] hyperinsulinemic clamp test; E–G, validation of our model regarding EGP (E), glucose appearance (F), and glucose half-life (t1⁄2) (F, inset) in gastrointestinal tract during OGTT: ■, calculated results; ▲, modeled values; □, data measured with double-tracer technique during 75-g OGTT in 12 subjects. Student’s t test: *, P ＜0.05 for females vs. males.

11. FIG. 2. Plasma concentrations (means ± SE) during OGTT (A–D) and the hyperinsulinemic clamp test (E–G) of glucose (A and E), insulin (B and F), C-peptide (C) and FFA (D and G) as well as clamp EGP (H) and M for total body weight (I) in females (○, n ＝48) and males (●, n ＝26). Student’s t test: *, P ＜0.05 for females vs. males.

12. FIG. 2. Plasma concentrations (means ± SE) during OGTT (A–D) and the hyperinsulinemic clamp test (E–G) of glucose (A and E), insulin (B and F), C-peptide (C) and FFA (D and G) as well as clamp EGP (H) and M for total body weight (I) in females (○, n ＝48) and males (●, n ＝26). Student’s t test: *, P ＜0.05 for females vs. males.

13. FIG. 3. A, ABS (milligrams per minute) averaged for each interval derived from mathematical modeling; B, amount of total glucose absorbed; C, relative glucose retention; in females (○, n ＝48) and males (●, n ＝26). Student’s t test: *, P <0.05; #, P <0.00001 for females vs. males.

14. FIG. 3. D, half-life of glucose (t1⁄2) in the gastrointestinal tract during the OGTT; E and F, relationship of glucose t1⁄2 with body height (E) and fat-free mass (F) in females (○, n ＝48) and males (●, n ＝26). Student’s t test: *, P <0.05; #, P <0.00001 for females vs. males.

15. Possible mechanisms We can only observe and analyze how glucose appears in the peripheral bed without evidence for what happens before its absorption. Thus, it is not easy to give reasons for the higher gut absorption velocity in taller persons, which could be because of 1) increased active transport capacity and/or 2) elevated intestinal surface area. By ingesting radioactive, chelated 111indium, it was shown that liquids empty from the stomach more slowly in women, with approximately 20 min reduced half-emptying time (31). This reflects the differences found in gut glucose t1⁄2 in this study. Thus, prolonged gastric emptying might contribute to slower glucose absorption. Alternatively, absorption may also be affected by mucosal surface, which, however, cannot be measured in intact humans. Of note, also calcium absorptive efficiency rises in taller persons (32). We totally agree with the suggestions by Barger-Lux and Heaney (32) that the effect of body size on absorptive kinetics is purely physical rather than physiological, because it appears likely that larger individuals have more intestinal surface for more rapid and efficient absorption. Regardless of the exact mechanism, our observations of an association between glucose absorption velocity and body size rather points from a gender-related effect on IGT incidence to the stronger influence of body tallness, which also differs between females and males. In all ethnic groups throughout the world, women are on average shorter than men (http://en.wikipedia.org/wiki/Human_height) by approximately 15 cm (33), like in this study (Table 1). Determination of body height in a single individual mostly results from genetic and environmental factors (34) but also from sexual dimorphism during pubertal growth with distinctions in GH secretion in response to sex steroid release (35, 36).

16. RESULTS Females showed lower (P <0.05) fasting EGP [1.4 ±0.1 mg/(kg ・min)] than males [1.7 ±0.1 mg/(kg ・min)] but comparable whole-body insulin sensitivity in clamp tests [females, 8.1 ±0.4 mg/(kg ・min); males, 8.3 ± 0.6 mg/(kg ・min)]. Plasma glucose OGTT concentrations were higher (P < 0.04)from30–40minin males butfrom120–180minin females. Glucose absorption rates were 21–46% increased in the initial 40 min in males but in females by 27–40% in the third hour (P <0.05). Gut glucose half-life was markedly higher in females (79 ±2 min) than in males (65 ±3 min, P <0.0001) and negatively related to body height (r = －0.481; P <0.0001).

17. CONCLUSIONS This study in healthy, glucose-tolerant humans shows for the first time different ABS rates during OGTT in women and men and a negative relationship between body height and gut glucose half-life. Prolonged ABS in females might therefore contribute to higher plasma glucose concentrations at the end of OGTT.

18. Message/Comments 経口投与のブドウ糖の吸収に男女差があるらしい。 （今はやりだと　インクレチンするのでは？）

20. Age Incretin Effect Beta CellFailure Lipotoxicity FFA 膵β細胞機能不全の病因 Genetics (TCF 7L2) Amyloid (IAPP) Deposition Insulin Resistance GlucoseToxicity

21. T2DMCandidate Polymorphisms • IGF2BP2　インスリンの作用を調整していると考えられているインスリン様成長因子2に関係する • CDKAL1β細胞に作用するタンパク質 • CDKN2AとCDKN2B β 細胞の成長に関与するタンパク質、ガンの成長でも研究されていた遺伝子 • TCF7L2β細胞の機能障害　インクレチンシグナル障害 • SCL30A8 β細胞だけで発現する亜鉛輸送体遺伝子 • KCNJ11　新生児糖尿病に関与 • HHEX • PPARα　脂肪酸化障害 • PPARγ • FTO　肥満 • GCKR中性脂肪を調節 • WFS1　インクレチンシグナル障害 • SLC30A8 • KCNQ1 • KCNJ15

22. Cecil JE et al. N Engl J Med 2008;359:2558-2566

23. Energy Expenditure in Carriers and Noncarriers of the A Allele Total energy expenditure was measured by means of the doubly labeled water method over a period of 10 days. A preisotope urine sample was obtained on day 0 for estimation of the unenriched isotope ratios of 18O and deuterium. After the sample was taken, the children were given an oral dose of labeled water (2H218O) in a low-calorie fruit juice. The juice was given at a dose of 0.15 g of 99% 2H2O (Sigma-Aldrich) per kilogram of body weight and 1.5 to 2.0 g of 10% H218O (Goss Scientific Instruments) per kilogram of body weight. Urine samples were collected 4 hours after dosing and then once daily on days 1 through 5 and on day 10. Cecil JE et al. N Engl J Med 2008;359:2558-2566

24. Energy Intake and Weight of Ingested Food at the Test Meal in Carriers and Noncarriers of the A Allele Cecil JE et al. N Engl J Med 2008;359:2558-2566

31. Abstract The quickening pace of genetic discovery has resulted in the identification of more than 80 loci with proven roles in development of monogenic and multifactorial forms of nonautoimmune diabetes and obesity.

32. Glossary Allele: One of two or more versions of a genetic sequence at a particular location in the genome. Association analysis: An approach to susceptibility-gene discovery that relies on identifying genetic variants whose allele frequencies are robustly correlated with either disease status or the level of a trait of interest. Candidate-gene study: An approach to susceptibility-variant discovery that focuses on genetic analysis restricted to one or more candidate genes — genes that have typically been selected on the basis of a perceived match between their known or presumed functions and the biologic characteristics of the disease in question. Coding variant: The part of the genomic DNA sequence that encodes proteins (consisting of approximately 1.5% of the total human genome). Genomewide association study: An approach used in genetics research to look for associations between many (typically hundreds of thousands) of specific genetic variations (most commonly, single-nucleotide polymorphisms) and particular diseases or traits. Homozygous: Having the same allele on both chromosomes at a particular location in the genome. Linkage analysis: An approach to susceptibility-gene discovery that relies on matching family-level patterns of segregation of the disease of interest with genetic markers of known location. Monogenic disease: Genetic disease attributable to variants with large effects on disease status. Because of the high penetrance of such variants, the disease typically cosegregates in a classic mendelian fashion (e.g., dominant or recessive). Next-generation sequencing: DNA sequencing that harnesses advances in miniaturization technology to simultaneously sequence multiple areas of the genome rapidly and at low cost. Noncoding variant: A DNA sequence variant that is located outside the coding sequence; some are likely to be involved in gene regulation. Syndromic disease: Syndromes are characterized by the concomitant occurrence of several distinct clinical features. In syndromic forms of diabetes such as Wolfram’s syndrome, a rare mutation of large effect leads not only to diabetes but also to a diversity of other features including optic atrophy and deafness. Transcript: An RNA sequence resulting from transcription of a DNA sequence (often a gene).

39. CONCLUSIONS The boundaries of personalized medicine will be much clearer in a few years, after large-scale genomewideresequencing efforts (now under way) provide a systematic, comprehensive description of the relations between genome sequence variation and major clinical phenotypes.

40. Message/Comments 糖尿病と診断したら、 遺伝子調べて治療を決めるようになるのだろうか？