Seventy-five gram glucose tolerance test to assess carbohydrate malabsorption and small bowel bacterial overgrowth.
OBJECTIVE
To investigate non-invasively the incidence of absorption of carbohydrates in diabetic patients during an oral glucose tolerance test (OGTT) and to determine whether malabsorption may be associated with insulin secretion and insulin resistance.


METHODS
A standard 75-g OGTT was performed in 82 diabetic patients. The patients received 75 g of anhydrous glucose in 225 mL of water after an overnight fasting and breath samples were collected at baseline and up to 120 min after ingestion. Breath hydrogen and methane concentrations were measured. Blood glucose and serum insulin concentrations were measured before ingestion and at 30, 60, 90, 120 min post-ingestion.


RESULTS
When carbohydrate malabsorption was defined as subjects with an increase of at least 10 ppm (parts per million) in hydrogen or methane excretion within a 2-h period, 28 (34%) had carbohydrate malabsorption. According to the result of increased breath test, 21 (75%) patients were classified as small bowel bacterial overgrowth and 7 (25%) as glucose malabsorption. Patients with carbohydrate malabsorption were older and had poor glycemic control as compared with those without carbohydrate malabsorption. The HOMA value, the sum of serum insulin during the test and the Delta insulin/Delta glucose ratio were greater in patients with carbohydrate malabsorption.


CONCLUSIONS
Insulin resistance may be overestimated by using these markers if the patient has carbohydrate malabsorption, or that carbohydrate malabsorption may be present prior to the development of insulin resistance. Hence carbohydrate malabsorption should be taken into account for estimating insulin resistance and beta-cell function.
Urita
Yoshihisa
Y
Department of General Medicine and Emergency Care, Toho University School of Medicine, Omori Hospital, Ota-Ku, Tokyo 143-8541, Japan. foo@eb.mbn.or.jp
Ishihara
Susumu
S
Akimoto
Tatsuo
T
Kato
Hiroto
H
Hara
Noriko
N
Honda
Yoshiko
Y
Nagai
Yoko
Y
Nakanishi
Kazushige
K
Shimada
Nagato
N
Sugimoto
Motonobu
M
Miki
Kazumasa
K
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001786:Blood Glucose / Q000032:analysis; D001944:Breath Tests; D050260:Carbohydrate Metabolism; D003924:Diabetes Mellitus, Type 2; D005189:False Positive Reactions; D005260:Female; D005951:Glucose Tolerance Test / Q000379:methods; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D015994:Incidence; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance / Q000502:physiology; D050417:Insulin-Secreting Cells / Q000502:physiology; D007408:Intestinal Absorption / Q000502:physiology; D007421:Intestine, Small / Q000382:microbiology* / Q000503:physiopathology*; D008286:Malabsorption Syndromes / Q000175:diagnosis / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D012016:Reference Values
D001786:Blood Glucose; D007328:Insulin