Dietary and lifestyle factors contributing to insulin resistance

Overweight and metabolic and hormonal parameter disruption are induced in adult male mice by manipulations during lactation period

Neonatal manipulations (10 min of maternal separation plus s.c. sham injection, daily for the first 21 d of life) determine overweight in male adult mice. In this work, we investigated the mechanisms underlying mild obesity and the alteration of caloric balance. Neonatally manipulated mice become overweight after onset of maturity, showing increased fat tissue and hypertrophic epididymal adipocytes. Increase in body weight occurs in the presence of a small increase in daily food intake (significant only in the adult period) and the absence of a decrease in spontaneous locomotor activity, while the calculated caloric efficiency is higher in manipulated mice, especially in adulthood. Fasting adult animals show hyperglycemia, hyperinsulinemia, hypertriglyceridemia, hypercholesterolemia, and hyperleptinemia. Soon after weaning and in the adulthood, plasma corticosterone and adrenocorticotropin (ACTH) are also significantly increased. Thus, neonatal manipulations in nongenetically susceptible male mice program mild obesity, with metabolic and hormonal alterations that are similar to those found in experimental models of diabetes mellitus, suggesting that this metabolic derangement may have at least part of its roots early on in life and, more interestingly, that psychological and nociceptive stimuli induce these features.

Early-life programming of susceptibility to dysregulation of glucose metabolism and the development of Type 2 diabetes mellitus

There is increasing epidemiological evidence in humans which associates low birthweight with later metabolic disorders, including insulin resistance and glucose intolerance. There is evidence that nutritional and hormonal factors (e.g. maternal protein restriction, exposure to excess maternal glucocorticoids) markedly influence intra-uterine growth and development. A picture is also emerging of the biochemical and physiological mechanisms that may underlie these effects. This review focuses on recent research directed towards understanding the molecular basis of the relationship between indices of poor early growth and the subsequent development of glucose intolerance and Type 2 diabetes mellitus using animal models that attempt to recreate the process of programming via an adverse intra-uterine or neonatal environment. Emphasis is on the chain of events and potential mechanisms by which adverse adaptations affect pancreatic-beta-cell insulin secretion and the sensitivity to insulin of key metabolic processes, including hepatic glucose production, skeletal-muscle glucose disposal and adipose-tissue lipolysis. Unravelling the molecular details involved in metabolic programming may provide new insights into the pathogenesis of impaired glucoregulation and Type 2 diabetes.

Exercise in diabetes management: maximizing benefits, controlling risks

Exercise is a recommended component of diabetes management. In both type 1 and type 2 diabetes mellitus, exercise can increase insulin sensitivity, lower blood glucose, and have positive psychological effects. More markedly in type 2 than in type 1, regular physical activity improves glycemic control, reduces hypertension, and normalizes lipids. Adjustments in insulin dosage, careful blood glucose monitoring, and attention to diet around the time of exercise will help prevent hypoglycemia and hyperglycemia, which are common hazards of exercise in type 1 diabetes. Special precautions are necessary for those who have diabetic complications such as retinopathy or peripheral neuropathy.

Captopril does not improve insulin action in essential hypertension: a double-blind placebo-controlled study

OBJECTIVE

To compare the effect of captopril with that of placebo on peripheral and hepatic insulin action in essential hypertension, in light of evidence that insulin resistance is associated with cardiovascular risk.

DESIGN

Randomized, double-blind, placebo-controlled, crossover trial, with 8 week treatment periods of captopril and placebo preceded and separated by 6 weeks of placebo.

SETTING

Belfast teaching hospital.

PATIENTS

Eighteen Caucasian nondiabetic patients (10 males), aged under 65 years, with essential hypertension, recruited from general practices in the greater Belfast area.

INTERVENTIONS

Captopril at 50 mg twice a day or placebo twice a day for two 8 week treatment periods.

MAIN OUTCOME MEASURES

Peripheral and hepatic insulin sensitivity assessed by glucose clamps.

RESULTS

Fourteen patients completed the study. Mean (+/- SEM) levels of fasting glucose, fasting insulin and postabsorptive hepatic glucose production were similar after captopril and placebo (5.4+/-0.1 versus 5.4+/-0.1 mmol/l, 10.6+/-2.2 versus 9.5+/-1.1 mU/l, 11.2+/-0.6 versus 11.0+/-0.5 mmol/kg per min, respectively). During hyperinsulinaemia, hepatic glucose production was suppressed to comparable levels after both treatments (4.8+/-0.6 versus 4.3+/-0.6 mmol/kg per min) and exogenous glucose infusion rates required to maintain euglycaemia were also similar (30.0+/-2.6 versus 30.3+/-2.6 mmol/kg per min).

CONCLUSION

Captopril therapy in uncomplicated essential hypertension has no effect on peripheral or hepatic insulin sensitivity.