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Biomedical subjects

N S Levitt

Publications and source records attributed to N S Levitt.

60 records · Page 4Linked to original sources
PubMed1980

Glucose-dependent insulin-releasing peptide in noninsulin-dependent maturity-onset diabetes: effects of autonomic neuropathy.

Glucose-dependent insulin-releasing peptide or gastric inhibitory polypeptide (GIP) is released into the circulation after ingestion of a mixed meal and is thought to enhance glucose-induced insulin release. We investigated basal and meal-stimulated GIP secretion in noninsulin-dependent maturity-onset diabetics (MODs). Twelve MODs and 12 healthy normal subjects were studied. Mean (+/- SE) basal plasma GIP concentrations were similar in MODs (297 +/- 34.5 pg/ml) and healthy subjects (305 +/- 29.7 pg/ml). Overnight insulin infusion normalized basal glucose levels in the MODs and induced a slight but insignificant rise in plasma GIP levels in MODs to 362 +/- 40.9 pg/ml; overnight gastric aspiration caused a further slight rise in basal GIP concentration to 392 +/- 56.6 pg/ml. The GIP responses to a mixed meal were significantly impaired at 90-240 min in MODs. The MODs were divided into 2 groups, each with 6 subjects: 1 group with autonomic neuropathy (AN) and the other without. The GIP responses in MODs without AN were similar to those in healthy subjects, but were significantly reduced in MODs with AN at all times after the meal. We suggest that the release of GIP after a meal is dependent upon the integrity of the autonomic nervous system; the mechanism may be related to the loss of autonomic control of gastric emptying or dependence of GIP secretion on autonomic modulation.

Adult↗
PubMedDate not supplied

The effect of dietary fiber on glucose and hormone responses to a mixed meal in normal subjects and in diabetic subjects with and without autonomic neuropathy.

We investigated the effects of fiber on responses of blood glucose, serum insulin, gastric inhibitory polypeptide (GIP), and immunoreactive pancreatic glucagon (IRG) to ingestion of mixed meal with and without added fiber (5 g guar and 5 g pectin) in 12 normal, healthy subjects and in 12 age-, sex-, and weight-matched non-insulin-dependent, maturity-onset diabetic subjects (NIDDM). Fiber markedly enhanced glucose tolerance in the normal subjects without a change in insulin or GIP but with a significant reduction in glucagon responses. Fiber also markedly improved glucose tolerance in the NIDDMs without changing insulin or GIP but with a significant reduction in the glucagon responses. The NIDDMs were divided into two groups of six subjects, with and without autonomic neuropathy (AN). In NIDDMs without AN, glucose tolerance was improved by fiber without a change in insulin, IRG, or GIP. In diabetic subjects with AN, glucose tolerance was not improved, although glucagon levels were lowered and insulin and GIP responses were unchanged. It appears, therefore, that fiber improves glucose tolerance by altering factors other than insulin. It seems also that autonomic nervous supply to the gastrointestinal tract is important in mediating the effect.

Blood Glucose↗
PubMedDate not supplied

Community-based tobacco control program: the Mamre study, a demonstration project.

OBJECTIVES: To assess the feasibility of a 5-year community-based tobacco control program in the community of Mamre in South Africa, while measuring the smoking and quitting rates at the beginning and end of this demonstration project. METHODS: A tobacco intervention program was developed at low cost in collaboration with the community, and involved a wide range of activities targeting people of all ages, especially those at risk for cardiovascular disease. Community members were trained to deliver smoking cessation programs and specific advice to smokers. Cross-sectional surveys were conducted in 1989 in a random sample of 1238 people, aged 15 years and older, prior to the 5-year demonstration project, and again in 1996 among 974 people at the end of the project. Demographic data and smoking and quitting patterns were collected by interviewer-administered questionnaires. Trained field workers used standardized procedures for recording blood pressure, height, and weight. RESULTS: The community participated with enthusiasm in the activities surrounding smoking cessation and the annual World No Smoking Day. The smoking rate decreased significantly between the two surveys (OR 1996/1989 = 0.82; 95% CI of 0.69-0.99), and the quitting rate increased significantly during the 5-year intervention period compared to the 5 years prior to the baseline survey (OR 1996/1989 = 0.74; 95% CI of 0.57-0.98). Men who participated in the program but continued to use tobacco in 1996 smoked more cigarettes than those who smoked in 1989. People who quit during the intervention period tended to be older, hypertensive, and obese; they consumed no alcohol, and noticed the health warnings posted in the community if they were older and had 10 or more years of education. CONCLUSIONS: A low-cost community-based tobacco control program was successfully implemented in the Mamre community. The program was received enthusiastically, built tobacco cessation skills, and significantly reduced the community's smoking rate compared to that before the demonstration project.

Adolescent↗
PubMedDate not supplied

Waist circumference predicts clustering of cardiovascular risk factors in older South Africans.

OBJECTIVE AND DESIGN: A cross-sectional analytical study to determine the cardiovascular risk factor profile of older residents of fishing villages on the West Coast of South Africa, and to determine which anthropometric measures are associated with risk factors. SUBJECTS: A convenient community-based sample of 152 subjects of mixed ancestry aged 55 years and over was recruited door-to-door using an address list of age-eligible subjects provided by the local public health care clinics. METHODS: Cardiovascular relationships were investigated between (i) number of risk factors (hypertension, hypercholesterolaemia, diabetes) and body mass index (BMI), waist-to-hip ratio (WHR), and waist circumference; and (ii) continuous cardiovascular risk factor variables and physical activity, smoking, dietary intake, and 24-hour urinary sodium and potassium concentrations. RESULTS: The prevalence of hypertension ( > or =160/95 mmHg) was 74.3% (95% CI: 67.2 - 81.4%). Neither 24-hour urinary sodium nor potassium concentrations was associated with blood pressure (BP). Past, but not present, moderate-intensity physical activity, particularly that associated with occupation, was negatively associated with systolic BP (r = -0.24, P < 0.05). The prevalence of diabetes and hypercholesterolaemia (serum cholesterol > or = 6.5 mmol/l) was 24.6% (95% CI: 17.2 - 32%) and 40% (95% CI: 31.8 - 48.2%), respectively. The percentage of subjects with 0, 1, or 2 or more cardiovascular risk factors was 13.4%, 44.1% and 42.5%, respectively. Subjects with a waist circumference > or = 92 cm had a significantly higher number of cardiovascular risk factors than those with a waist circumference < 92 cm ( chi(2) = 9.29, P < 0.01), and this association remained significant even after controlling for age, sex and smoking (P < 0.05). Neither BMI tertiles according to sex, nor a BMI cut-point > or =30, was significantly associated with a clustering of risk factors. CONCLUSION: In a sample of older South Africans of mixed ancestry at high risk of cardiovascular disease, waist circumference measuring > or = 92 cm predicts clustering of risks factors, independently of BMI. This simple, population-specific reference value may provide a useful screening tool to identify at-risk individuals for targeted prevention for coronary heart disease and associated metabolic disorders.

Abdomen↗