Lactase deficiency and lactose malabsorption. A review

The results of previous investigations of lactase deficiency and lactose malabsorption are reviewed. It showed that lactase activity and its decline in animals and humans is controlled genetically, but also that its phenotypic expression as lactose malabsorption is influenced by nongenetic factors: adaptation, biological (circadian) rhythmicity, hormones, gastrointestinal functions, and nutritional components can alter the response to lactose intake.     

Vagal tone and meal-induced abdominal symptoms in healthy subjects

BACKGROUND/AIMS: Patients with functional dyspepsia often have meal-induced dyspeptic symptoms and low vagal tone. We examined whether these variables are related in healthy subjects. METHODOLOGY: In 40 healthy subjects vagal tone and abdominal symptoms were recorded before and after a 500-ml soup meal ingested in 1 and 4 min on separate visits. Vagal tone was indexed by respiratory sinus arrhythmia (RSA). RESULTS: Scores for nausea and discomfort were higher when the soup was ingested in 1 min as compared with 4 min (nausea: p = 0.02; discomfort: p = 0.04). There was no difference in fullness or abdominal pain. RSA was unrelated to meal-induced symptom scores. RSA varied with respiration and body position: It was highest while breathing deeply in the sitting position (24.0 beats/min). With normal breathing RSA was highest in the supine position (9.0 beats/min), lower while sitting (7.0 beats/min) and lowest while standing (6.2 beats/min). CONCLUSIONS: Epigastric discomfort in response to rapid ingestion of a test meal in healthy subjects was not related to vagal tone as indexed by RSA. Vagal tone varied with breathing pattern and body position. It is possible that increasing vagal tone by such measures can be beneficial in the treatment of patients with functional dyspepsia.     

Lactase deficiency: somatoneurology and neurodietology

Neurologic and somatoneurologic aspects of lactose intolerance are considered in the article. Authors stress the role of adequate diet therapy in this form of food intolerance.     

Lactase deficiency in Singapore-born and Canadian-born Chinese

Seventy-three of 77 adult Singapore-born Chinese (95%) and 48 of 49 Canadian-born adult Chinese (98%) were demonstrated to be lactase deficient using the lactose breath hydrogen test. The similar prevalence of lactase deficiency in the Singapore- and the Canadian-born Chinese despite a larger estimated amount of daily milk ingestion in the Canadian-born Chinese (430 ml vs 157 ml) supports the concept that lactase deficiency, which is transmitted genetically, does not have an adaptable component related to the quantity of lactose ingested. When the lactose breath hydrogen test performed with a dose of 0.5 g/kg of lactose was compared with the test using a standard dose of 50 g of lactose, there was very little loss of sensitivity. In spite of the presence of lactase deficiency, only 32% of the Singapore subjects and 23% of the Canadian subjects had gastrointestinal symptoms when milk was ingested in the daily diet. Peak breath H₂ was higher in females than males, but the difference was more significant in the Canadian cohort.     

Lactase deficiency in Jewish communities in Israel

Lactase deficiency and lactose tolerance were studied in several Jewish communities in Israel. Lactase deficiency was found in 60% of biopsied subjects. Forty-one biopsies were peroral and 22, surgical; histologically, the jejunal mucosa of all specimens was normal. Lactose tolerance tests were performed on 217 subjects, 118 patients and 99normals. A low glucose rise was found in 44.4% of Yemenites, 62.5% of North Africans (Sephardi), 72.2% of others (Sephardi), 79.2% of Ashkenazi, 84.2% of Iraqis and 85.0% of others (Oriental); the overall incidence was 71.1%. Statistical analysis confirmed that the population studied was heterogenous. Most subjects with a low glucose rise had symptoms during the test. Milk intake, low in almost all subjects, did not correlate with lactose tolerance. Most lactose intolerant subjects were not aware of milk intolerance; the condition is not usually symptomatic in Israel. Lactase deficiency in various population groups has been reviewed and evidence in favor of a genetic etiology emphasized.The authors wish to thank the staff of the Tel-Aviv Government Municipal Hospitals, in particular, the Department of Pediatrics-B for their help in carrying out this investigation and for permission to study their patients; Dr. A. Adam, Department of Human Genetics, Tel-Aviv University Medical School, for helpful advice and criticism. Blood sugar estimations were performed at the Central Biochemical Laboratory of the Workers Sick Fund, Tel-Aviv.     

QT interval in 24-hour ambulatory ECG recordings from 60 healthy adult subjects

QT and RR intervals were measured in 24-hour electrocardiographic (ECG) recordings from 60 healthy subjects randomly selected among participants in the Copenhagen City Heart Study. Five men and five women of each 10-year age group between the ages of 20 and 79 were included. The mean of three consecutive RR and QT intervals was calculated from ECG strips recorded at 1000, 1400, 1800, 2200, 0200, and 0600 hours in each subject. The RR interval varied between 728 ms at 1400 hours and 984 ms at 0600 hours, and the uncorrected QT interval between 358 ms at 1400 hours and 417 ms at 0200 hours. The QT interval corrected for heart rate by Bazett's formula varied between 418 ms at 0600 hours and 428 ms at 1000 hours, and the QT interval corrected by the regression equation of this study varied between 396 ms at 1400 hours and 422 ms at 0200 hours. Multiple regression analysis of uncorrected data yielded a partial regression coefficient for heart rate influence of 0.14. After correction by Bazett's formula, a statistically significant effect of heart rate remained (partial regression coefficient -0.08, t = -9.93, p less than 0.0001). In addition to the influence of heart rate, the analysis revealed a statistically significant effect of hour of day (F = 11.30; DF 5, 286; p less than 0.0001) and gender (F = 6.24; DF 1, 53; p less than 0.05), whereas age in the range of 20-79 years had no significant effect. The QT intervals of this study differed from the values measured in standard ECG recordings but not from those of other Holter studies.(ABSTRACT TRUNCATED AT 250 WORDS)     

Serum glucose concentration and ACP1 genotype in healthy adult subjects

Acid phosphatase locus 1 (ACP 1 ) or cytosolic low molecular weight protein tyrosine phosphatase is a polymorphic enzyme that can hydrolyze phosphotyrosine-containing peptides of the human insulin receptor and of band 3 protein. High-activity ACP 1 may favor an increase in serum glucose concentration through a depression of insulin action and through inactivation of aldolase, phosphofructokinase, and glyceraldehyde-3-phosphate dehydrogenase induced by dephosphorylation of band 3 protein. In diabetic subjects, we have previously reported lower serum glucose concentration in subjects with low-activity ACP 1 A and AB phenotypes. We have now studied the relationship between serum glucose concentration and ACP 1 genotype in a sample of 137 healthy adult workers of our university. In males, serum glucose concentration is significantly higher in medium-high- than in low-activity ACP 1 genotypes. With advancing age in males, there is a progressive increase in glycemic differential between medium-high- and low-activity ACP 1 genotypes. The data suggest that normal variability of ACP 1 genotype influences serum glucose concentration in normal individuals. Such influence depends on sex and in males becomes more marked with advancing age.     

Gastric emptying of lactose and milk in subjects with lactose malabsorption

Six lactose absorbers (LA) and 5 lactose malabsorbers (LM) had tests of gastric emptying with 750-ml meals of glucose in water, lactose in water, plain milk, and chocolate milk. The glucose and lactose meals emptied in a similar fashion in LA and LM subjects with a significant decrease in gastric emptying as the osmolarity of the meals was doubled. If the data are normalized by dividing lactose emptying by the emptying of glucose meals of twice the osmolality in each individual, the lactose malabsorbers empty significantly more lactose. Both LA and LM subjects emptied comparable amounts of milk meals having similar osmolarity. Chocolate milk, which had a higher osmolality than plain milk, emptied more slowly than plain milk in both groups, and this difference was significant in the LM group.     

Ornithine transcarbamylase deficiency: adult onset of severe symptoms

Deficiency of ornithine transcarbamylase, an enzyme in the urea cycle, results in hyperammonemia. The X-linked recessive inheritance results in neonatal death of affected males but a variable symptomatic pattern in females, with onset of symptoms in childhood. We report the cases of two heterozygous women with onset of severe symptoms (encephalopathy and focal neurologic deficits) in adulthood.     

老年入及慢性非器质性腹泻患者的乳糖酶缺乏症

用乳糖氢呼吸试验检测了18例20～65岁正常人基础氢值均在30PPM以下,平均22.5±3.8PPM,服乳糖后氢上升≥20PPM者13例(72.2％),平均升高62.9±64.4MMP。基本健康的70～87岁老人共17例,基础氢值19.7±4.0PPM,乳糖试验异常者7例(41.1％),呼气中氢平均升高42.4±23.6PPM。21例非器质性慢性腹泻患者基础氢平均22.7±9.0PPM,有2例>30PPM,服乳糖后异常者18例(85.7％),平均升高60.4±34.5PPM。说明我国正常人中乳糖酶缺乏的阳性率约为72.2％。高龄老人中阳性率41.1％,有随年龄增高逐渐适应的趋势。非器质性腹泻组乳糖酶缺乏的阳性率85.7％,且有2例空腹氢含量升高,提示乳糖酶缺乏可能与部份慢性腹泻患者的病因有关,这类病人在症状发作期间限制乳类制品是值得推荐的。     

Comparison between serum interleukin-2 concentrations in healthy adult and elderly subjects

The serum interleukin-2 (IL-2) concentrations were evaluated in healthy elderly patients, enrolled under the SENIEUR protocol, and healthy adult controls. The aim of the study was to ascertain whether the reduced immune response, described during aging, is linked to deficient production of IL-2 or to its receptorial deficit, or if the reduced serum IL-2 concentrations observed during aging can be used as a biological immunodeficiency marker. The results obtained did not show any significant differences between the study groups, even if mean values were slightly decreased in the elderly group, as compared to the adult one. This finding does not justify the age-dependent deficiency of the immune response, i.e., to explain this condition, one needs another pathogenetic hypothesis. It is suggested that one such hypothesis could be the alteration of IL-2 receptors which undergo major cleavage and minor re-expression in the elderly, causing this way some receptorial changes with consequent reduction of T-helper activation.     

Ethnicity affects IGFBP-3 and IGF-II in normal healthy young adult subjects

OBJECTIVE  While the effects of age on the growth hormone/insulin-like growth factor (IGF) axis are well documented, the influence of ethnic background is unknown. The differences in IGF and IGF binding proteins (IGFBPs) were investigated in two ethnic groups.
DESIGN  A cross-sectional study of an age-selected cohort of healthy, normoglycaemic, non-obese Caucasian (C) and Asian (A) subjects.
PATIENTS  Fifty-three (27 C, 26 A) subjects with a mean age (±SD) of 20.6±0.8 years were studied.
MEASUREMENTS  Fasting measurements of glucose, insulin, IGF-I, IGF-II, IGFBP-1 and IGFBP-3. Western ligand blotting and immunoblotting with IGFBP-2 and IGFBP-3 of serum samples.
RESULTS  There were no significant differences in IGF-I levels between Caucasian and Asian subjects (C 218±55 vs A 229±40μg/l; P =0.44). IGF-II (C 707±110 vs A 583±75μg/l; P <0.0001) and IGFBP-3 (C 5.9±1.2 vs A 5.12±1.17 mg/l; P =0.01) levels were significantly higher in Caucasian subjects. Immunoblotting of ligand blots revealed no protease activity on either IGFBP-3 or IGFBP-2 to account for these ethnic differences.
CONCLUSIONS  Ethnic differences in IGFBP-3 and associated IGF-II levels may affect the inter-relationships of IGFs and their binding proteins and need to be considered when interpreting IGF data on growth and metabolism.     

Frequency of Helicobacter pylori and gastritis in healthy subjects without gastrointestinal symptoms.

To investigate the frequency of Helicobacter pylori and gastritis in asymptomatic adults, 30 healthy volunteers underwent upper endoscopy. Biopsy specimens were obtained from the corporeal and antral mucosa of the stomach. The specimens were examined by light microscopy for gastritis and the occurrence of H. pylori. In 12 subjects signs of gastritis were noted at endoscopy, but only in 7 of them was this diagnosis confirmed histologically. No other abnormalities were observed by the endoscopist. Histologic examination was normal in 17 subjects, but in 13 subjects (43%) inflammation was found in the gastric specimens. Ten had inflammation both in the corpus and in the prepyloric specimens, and in six of these subjects H. pylori was discovered. H. pylori was only found in subjects with inflammation in both the corpus and the antrum. Subjects with gastritis were slightly older than subjects with normal gastric mucosa (median age, 47 versus 37 years; not significant). In the group of subjects with gastritis, persons with H. pylori were older than those without (median age, 53.5 versus 36 years; p = 0.05). The results of our study indicate that gastritis is present before colonization with H. pylori occurs. This could imply that H. pylori is not the cause of gastritis but that the presence of gastritis is a prerequisite for colonization of the bacterium in the stomach.     

Steady-state plasma and intrapulmonary concentrations of levofloxacin and ciprofloxacin in healthy adult subjects

STUDY OBJECTIVE: To determine the steady-state plasma, epithelial lining fluid (ELF), and alveolar macrophage (AM) concentrations of levofloxacin and ciprofloxacin. DESIGN: Multiple-dose, open-label, randomized pharmacokinetic study. PARTICIPANTS: Thirty-six healthy, nonsmoking adult subjects were randomized either to oral levofloxacin, 500 or 750 mg once daily for five doses, or ciprofloxacin, 500 mg q12h for nine doses. INTERVENTIONS: Venipuncture, bronchoscopy, and BAL were performed in each subject at 4 h, 12 h, or 24 h after the last administered dose of antibiotic. MEASUREMENT AND RESULTS: Mean plasma concentrations of levofloxacin and ciprofloxacin were similar to those previously reported. For once-daily dosing of levofloxacin, 500 mg, the mean (+/- SD) steady-state concentrations at 4 h, 12 h, and 24 h in ELF were 9.9 +/- 2.7 microg/mL, 6.5 +/- 2.5 microg/mL, and 0.7 +/- 0.4 microg/mL, respectively; AM concentrations were 97.9 +/- 80.0 microg/mL, 36.7 +/- 23.4 microg/mL, and 13.8 +/- 16.0 microg/mL, respectively. For levofloxacin, 750 mg, the mean steady-state concentrations in ELF were 22.1 +/- 14.9 microg/mL, 9.2 +/- 5.3 microg/mL, and 1.5 +/- 0.8 microg/mL, respectively; AM concentrations were 105.1 +/- 65.5 microg/mL, 36.2 +/- 26.1 microg/mL, and 15.1 +/- 2.0 microg/mL, respectively. The concentrations of ciprofloxacin at 4 h and 12 h in ELF were 1.9 +/- 0.9 microg/mL and 0.4 +/- 0.1 microg/mL, respectively; AM concentrations were 34.9 +/- 23.2 microg/mL and 6.8 +/- 5.9 microg/mL, respectively. The differences in the ELF concentrations of the two levofloxacin groups vs those of the ciprofloxacin group were significant (p < 0.05) at each sampling time. CONCLUSIONS: Levofloxacin was more extensively distributed into intrapulmonary compartments than ciprofloxacin and achieved significantly higher steady-state concentrations in plasma and ELF during the 24 h after drug administration.     

Prediction of the maximal voluntary ventilation in healthy adult Chinese subjects

OBJECTIVES: The aim of the present study was to investigate the relationship between the FEV(1) and maximal voluntary ventilation (MVV) in healthy adult Chinese subjects, and to determine the validity of existing prediction equations of MVV for use in the Chinese population. METHODOLOGY: Ninety-five healthy subjects (48 male and 47 female) stratified into five age groups (from 20 to 70 years) for both sexes were recruited from the general population. The FEV(1) and MVV of these subjects were measured with a clinical spirometer. The MVV was determined using the closed-circuit technique. The MVV was assessed for 12 s and values were calculated to obtain L/min. Multiple regression analysis was used to develop equations to predict MVV with age, height, FEV(1) as well as with FEV(1) alone as predictor variables. One-sample t-tests were used to compare the actual values of MVV for the subjects with their predicted values using equations from previous studies of MVV in healthy subjects. RESULTS: Using FEV(1) only, the following predictive equation was obtained: MVV = FEV(1) x 45.12 - 15.85 (adjusted r(2) = 0.792). Predicted MVV values using previously cited equations, including MVV = FEV(1) x 35 or 40, were all significantly different from the actual MVV values of these subjects. CONCLUSIONS: The relationship between MVV and FEV(1) among healthy adult Chinese subjects is described. Previously cited equations describing the relationship between FEV(1) and MVV cannot be applied to healthy adult Chinese subjects.