Association between blood pressure and insulin resistance in obese females during weight loss and weight rebound phenomenon

Comprehensive laboratory reference intervals for routine biochemical markers and pro-oxidant-antioxidant balance (PAB) in male adults

Background

Reference values of biochemical markers are influenced by various parameters including age, sex, region, and lifestyle. Hence, we aimed to determine age‐ and BMI‐specific reference intervals (RIs) for important clinical biomarkers in a healthy adult male population from northeastern Iran. This is also the first study to investigate reference values for pro‐oxidant‐antioxidant balance (PAB).

Methods

Seven hundred and twenty (720) healthy men, aged 20‐60 years, were recruited from Sarakhs in the northeast region of Iran. Reference values for lipid profiles (total cholesterol, triglyceride, HDL‐C and LDL‐C), fasting blood glucose, inflammatory factors (hs‐CRP and PAB), minerals (zinc and copper), uric acid, and blood pressure were measured and statistically analyzed to establish accurate age‐ and BMI‐specific RIs in alignment with CLSI Ep28‐A3 guidelines.

Results

RIs for lipid profiles, inflammatory factors, minerals, and uric acid required no age partitioning with the exception of fasting blood glucose and blood pressure, which demonstrated significantly higher values in subjects aged 50 years and older. Among these biomarkers, only uric acid, blood pressure, and triglycerides demonstrated statistically significant increases in reference value concentrations with increasing BMI.

Conclusion

In this study, age‐ and BMI‐specific RIs for several biochemical markers were determined in healthy adult Iranian men. Partitioning by age and BMI was only required for a few analytes with most demonstrating no statistically significant changes with these covariates. These data can be useful to monitor various diseases in male adults with varying BMI in this region and others.

Effect of regular swimming exercise on the physical composition, strength, and blood lipid of middle-aged women

The purpose of this study is to define the effects of regular swimming exercise on the physical composition, physical strength, and blood lipids of middle-aged women. The subjects of this study are a total of 24 middle-aged women in the swimming group and the control group, with 12 women for each group. The swimming group performed swimming exercise for 60 min every time for 3 times a week, for a total of 12 weeks. For data processing, SPSS 21.0 statistics program was used to calculate the mean and standard deviation. For the difference verification on the change in mean for each group and between the groups, paired and independent t-tests were respectively used. As a result, for physical composition, the body fat rate decreased in the swimming group. Moreover, the difference verification result showed a statistically significant difference between the groups. For physical strength, the difference verification result for each group showed that the swimming group had a statistically significant difference in flexibility and cardiovascular endurance. Moreover, the difference verification result between the groups showed a statistically significant difference only for flexibility. For blood lipids, as a result of the difference verification for each group, T-C and TG showed a significant decrease, and HDL-C, a significant increase. However, in the difference verification result between the groups, only T-C and TG showed a statistically significant difference. With these results, it is considered that regular swimming exercise is effective for improving the physical composition, physical strength, and blood lipids of middle-aged women.

Healthy strategies for successful weight loss and weight maintenance: a systematic review

The rates of overweight and obesity are rising in Canada and worldwide, and there is a need for effective methods for weight loss and weight maintenance to empower individuals to make changes. The purpose of this systematic review was to examine the evidence available for successful diet strategies for weight loss and weight maintenance among adults. A search was conducted of the following databases: CAB Abstracts, Central Register of Controlled Trials, EMBASE, MEDLINE, Food Science and Technology Abstracts, and Web of Knowledge. The studies investigated had participants who were overweight or obese and between 18 and 65 years of age. A successful study was defined as one that reported an intervention that created ≥5% weight loss from baseline and a maintenance phase during which the ≥5% weight loss was maintained from baseline to 12 months. After exclusions, the search resulted in 67 papers. Overall, for significant safe weight loss, an energy deficit was required, which was commonly achieved by reduced fat intake. Increased dietary fibre was also a component of 21% of successful interventions. Physical activity was included in 88% of successful interventions, and behaviour training such as self-monitoring was part of 92% of successful interventions. The same combination of energy and fat restriction, regular physical activity, and behavioural strategies was also required for successful weight maintenance. This review confirmed previous knowledge about weight loss and weight maintenance in adults. A comprehensive approach, including reduced dietary intake, regular physical activity, and behavioural strategies, is warranted and is supported by the research evidence.

Fasting insulin level is positively associated with incidence of hypertension among American young adults: a 20-year follow-up study

OBJECTIVE

Although hyperinsulinemia, a surrogate of insulin resistance, may play a role in the pathogenesis of hypertension (HTN), the longitudinal association between fasting insulin level and HTN development is still controversial. We examined the relation between fasting insulin and incidence of HTN in a large prospective cohort.

RESEARCH DESIGN AND METHODS

A prospective cohort of 3,413 Americans, aged 18-30 years, without HTN in 1985 (baseline) were enrolled. Six follow-ups were conducted in 1987, 1990, 1992, 1995, 2000, and 2005. Fasting insulin and glucose levels were assessed by a radioimmunoassay and hexokinase method, respectively. Cox proportional hazards models were used to calculate hazard ratios (HRs) and 95% CIs of incident HTN (defined as the initiation of antihypertensive medication, systolic blood pressure ≥140 mmHg, or diastolic blood pressure ≥90 mmHg).

RESULTS

During the 20-year follow-up, 796 incident cases were identified. After adjustment for potential confounders, participants in the highest quartile of insulin levels had a significantly higher incidence of HTN (HR 1.85 [95% CI 1.42-2.40]; P(trend) < 0.001) compared with those in the lowest quartile. The positive association persisted in each sex/ethnicity/weight status subgroup. A similar dose-response relation was observed when insulin-to-glucose ratio or homeostatic model assessment of insulin resistance was used as exposure.

CONCLUSIONS

Fasting serum insulin levels or hyperinsulinemia in young adulthood was positively associated with incidence of HTN later in life for both men and women, African Americans and Caucasians, and those with normal weight and overweight. Our findings suggested that fasting insulin ascertainment may help clinicians identify those at high risk of HTN.

The effect of body mass index and fasting glucose on the relationship between blood pressure and incident diabetes mellitus: a 5-year follow-up study

There is no consensus on the relationship between high blood pressure (BP) and incident diabetes mellitus (DM). Therefore, the aim of the current study was to investigate the independent association between BP and incident DM and identify the metabolic components that influence incident DM in Korean subjects. The current study included 14 054 non-diabetic subjects (mean age of 41 years) at the start of the study who were followed for an average of 5 years. We measured the risk for incident DM according to the subjects' baseline BP. Subjects were separated into three groups as follows: normotensive (<120/80 mm Hg), pre-hypertensive (120/80 mm Hg ⩽BP <140/90 mm Hg) and hypertensive (⩾140/90 mm Hg). The overall incidence of DM was 1.8% (246 subjects), comprising 0.9% of the normotensive group, 1.9% of the pre-hypertensive group and 4.0% of the hypertensive group (P<0.01). Within the hypertensive group, subjects with high body mass index (BMI) and high fasting-glucose levels were 40 times more likely to develop DM compared with those with low BMI and low glucose levels (0.3 vs. 13.2%, P=0.001). The risk for incident DM was significantly higher in the hypertensive group compared with that in the normotensive group (OR 3.41 vs. 1.00, P<0.0001). However, the significance disappeared after making adjustments for the baseline BMI and fasting glucose levels (OR 1.18 vs. 1.00, P=0.83). We found that the significance of high BP in predicting incident DM was influenced by the baseline BMI and fasting glucose levels of the subjects.

Insulin Resistance and Hypertension: Seven-Year Follow-Up Study in Middle-Aged Japanese Men (the KEIO Study)

Only a few longitudinal studies in Asians have shown a close association between hyperinsulinemia and the incidence of hypertension. In the present study, we used the insulin resistance index, HOMA-IR [fasting plasma glucose (FPG) (mmol/l) X insulin (microUl/ml) / 22.5], and tried to elucidate longitudinally the relationship among insulin resistance, blood pressure, body mass index (BMI), FPG, and lipid profile in middle-aged Japanese men. Three hundred and ten male non-hypertensive subjects aged 30 to 58 years in 1993 (44.5 +/- 7.8 (SD) years; BMI, 22.6 +/- 2.5 kg/m2) were divided into three groups according to HOMA-IR (A: lowest; B: middle; and C: highest). Their BMI, systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate, FPG and lipid profile were followed up for 7 years. The percentage of high normal blood pressure in 1993 and 2000 did not differ among the three groups. However, in 2000 hypertensive subjects made up 11.7% of group A (12/103), 15.4% of group B (16/104), and 29.1% of group C (30/103) (chi2 = 11.50, p = 0.003). SBP, DBP, and many other metabolic parameters in 2000 were significantly higher in group C than in the other groups. Furthermore, both SBP and DBP in 2000 were positively correlated with HOMA-IR in 1993 (r = 0.17 and p < 0.01 for both). The correlation between HOMA-IR in 1993 and DBP in 2000 was significant, even after adjustment for age and BMI in 1993. These findings suggest an important role of insulin resistance in predicting the future incidence of hypertension in middle-aged Japanese men.

Impact of multiple risk factor clustering on the elevation of blood pressure

A family history of hypertension, obesity, diabetes mellitus, hypercholesterolemia, and hypertriglyceridemia have all been associated with risk of hypertension. We retrospectively conducted a longitudinal study in a large screened cohort to explore the effect of the clustering of these five risk factors on the elevation of blood pressure (BP) in normotensive subjects at baseline. The study group comprised 4,857 normotensive subjects not treated with antihypertensive drugs (systolic BP < 140 mmHg, diastolic BP < 90 mmHg, 3,111 men and 1,746 women) who were followed up from 1997 to 1999. By 1999, 360 subjects had BP at the hypertensive level (systolic BP > or = 140 mmHg or diastolic BP > or = 90 mmHg). The incidence of subjects whose BP became hypertensive was 37 per 1,000 person-years. After adjusting for age, sex, systolic BP and other clinical factors, multiple logistic analysis showed that the relative risk of BP elevation was 1.49 (95% Cl: 1.09 to 2.05) in subjects with one risk factor; 1.65 (95% Cl: 1.15 to 2.27) in those with two risk factors; 1.42 (95% Cl: 0.91 to 2.32) in those with three; and 4.86 (95% Cl: 2.58 to 9.16) in those with four or more when compared with subjects with no risk factors. Multiple regression analysis showed that the number of risk factors was positively correlated with an increase in BP from 1997 to 1999; the regression coefficient was 0.51 (p = 0.001) for increase in systolic BP, and 0.31 (p = 0.008) for increase in diastolic BP after adjusting for age and sex. In conclusion, clustering of risk factors significantly predicted the development of hypertension.

Relationship between changes in serum leptin levels and blood pressure after weight loss

Insulin resistance is thought to raise blood pressure. Recently, a significant positive relationship between mean blood pressure and plasma leptin levels, but there have been no reports dealing with the relationship between blood pressure and either insulin resistance or serum leptin levels after weight loss. In the present work, we attempted to clarify the relationship between changes in blood pressure and either the serum leptin level or the insulin level in 102 moderately obese females (mean body mass index (BMI), 29.5 +/- 0.5 kg/m2; age, 47.0 +/- 0.9) during a 3 month period. No differences in age, fat-mass, homeostasis model assessment (HOMA), the summation of insulin (sigmaIRI), plasma renin activity (PRA) or 24 h norepinephrine excretion (24hU-NE) were observed between the hypertensive (HT) group (n = 31) and normotensive (NT) group (n = 71) before weight loss, but the basal serum leptin was significantly higher in the HT (16.8 +/- 1.1 ng/ml) than in the NT group (15.2 +/- 0.8 ng/ml), after adjusting for abdominal total fat. After a 3 month weight reduction program, the total abdominal fat, serum leptin and sigmaIRI significantly decreased in both groups. The systolic blood pressure (SBP)/diastolic blood pressure (DBP) significantly decreased from 144/84 to 130/77 mmHg only in the HT but not in the NT group. The PRA decreased in both groups, while the 24hU-NE significantly decreased only in the HT group. The changes in the leptin level were significantly correlated with the changes in both sigmaIRI and HOMA after weight loss in the two groups, respectively. Finally, a statistically significant positive correlation was observed between the changes in the leptin and the changes in the mean blood pressure (MBP) (r = 0.412, p < 0.05) only in the HT group. Multiple regression analysis revealed that the changes in MBP were independently associated with the changes in 24hU-NE and the changes in either sigmaIRI or HOMA in all subjects. However, a statistically significant positive correlation was observed between the changes in MBP and the changes in leptin levels even after adjusting for the total abdominal fat, 24hU-NE and either sigmaIRI or HOMA (both expressed as a percentage of the baseline value) in a multiple regression analysis only in the HT group. These results suggest that leptin may play a role in the pathophysiology of obese hypertension.

Emerging concepts in the pathophysiology and treatment of obesity-associated hypertension

The dramatic increase in the prevalence of obesity is a global phenomenon associated with increased risk of the development of cardiovascular and renal disease. Changes in renal structure and function that occur early in the development of obesity may lead to urine outflow obstruction and increased intrarenal pressure, mechanisms sufficient to shift the pressure-natriuresis relation to higher blood pressure levels. Another important alteration that may lead to hypertension with obesity is the increase in sympathetic nervous system activity. Several studies point to higher leptin levels associated with hypertension in humans, and animal data now convincingly suggest that leptin has direct central effects that increase sympathetic outflow to the kidneys, associated with increases in blood pressure. Although understanding of the pathophysiology of obesity-associated hypertension has made substantial progress during the past years, treatment of obese hypertensives remains largely empirical and clearly deserves to be addressed in larger randomized, controlled trials.