Serum Lipids During 20 Years in the Tehran Lipid and Glucose Study: Prevalence, Trends and Impact on Non-Communicable Diseases

The Tehran longitudinal family-based cardiometabolic cohort study sheds new light on dyslipidemia transmission patterns

Dyslipidemia, as a metabolic risk factor, with the strongest and most heritable independent cause of cardiovascular diseases worldwide. We investigated the familial transmission patterns of dyslipidemia through a longitudinal family-based cohort, the Tehran Cardiometabolic Genetic Study (TCGS) in Iran. We enrolled 18,729 individuals (45% were males) aged > 18 years (mean: 38.15 (15.82)) and observed them over five 3-year follow-up periods. We evaluated the serum concentrations of total cholesterol, triglyceride, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol with the first measurement among longitudinal measures and the average measurements (AM) of the five periods. Heritability analysis was conducted using a mixed-effect framework with likelihood-based and Bayesian approaches. The periodic prevalence and heritability of dyslipidemia were estimated to be 65.7 and 42%, respectively. The likelihood of an individual having at least one dyslipidemic parent reveals an OR = 6.94 (CI 5.28-9.30) compared to those who do not have dyslipidemic parents. The most considerable intraclass correlation of family members was for the same-sex siblings, with ICC ~ 25.5%. For serum concentrations, heritability ranged from 33.64 to 60.95%. Taken together, these findings demonstrate that familial transmission of dyslipidemia in the Tehran population is strong, especially within the same-gender siblings. According to previous reports, the heritability of dyslipidemia in this population is considerably higher than the global average.

Epidemiology and Prevalence of Dyslipidemia Among Adult Population of Tehran: The Tehran Cohort Study

BACKGROUND

Dyslipidemia is among the leading risk factors for cardiovascular diseases (CVDs), with an increasing global burden, especially in developing countries. We investigated the prevalence of dyslipidemia and abnormal lipid profiles in Tehran.

METHODS

We used data from 8072 individuals aged≥35 from the Tehran Cohort Study (TeCS) recruitment phase. Fasting serum total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-C), high-density lipoprotein-cholesterol (HDL-C), and triglyceride were measured. Dyslipidemia was defined according to the National Cholesterol Education Program Adult Treatment Panel III criteria, and high LDL/HDL was defined as a ratio>2.5. The age-sex standardized prevalence rates were calculated based on the 2016 national census. Furthermore, the geographical distribution of dyslipidemia and lipid abnormalities was investigated across Tehran's zip code districts.

RESULTS

The age-sex standardized prevalence was 82.7% (95% CI: 80.1%, 85.0%) for dyslipidemia, 36.9% (95% CI: 33.8%, 40.1%) for hypertriglyceridemia, 22.5% (95% CI: 19.9%, 25.4%) for hypercholesterolemia, 29.0% (95% CI: 26.1%, 32.1%) for high LDL-C, 55.9% (95% CI: 52.6%, 59.2%) for low HDL-C, and 54.1% (95% CI: 50.9%, 57.3%) for high LDL/HDL ratio in the Tehran adult population. The prevalence of dyslipidemia, low HDL-C, and high LDL/HDL ratio was higher in the northern regions, hypercholesterolemia was higher in the southern half, and high LDL-C was more prevalent in the middle-northern and southern areas of Tehran.

CONCLUSION

We found a high prevalence of dyslipidemia, mainly high LDL/HDL in the Tehran adult population. This dyslipidemia profiling provides important information for public health policy to improve preventive interventions and reduce dyslipidemiarelated morbidity and mortality in the future.

Association Between HDL2-C and HDL3-C with Cardiovascular Disease: A Nested Case-Control Study in an Iranian Population

Background

The contribution of high-density lipoprotein cholesterol (HDL-C) subclasses to incident cardiovascular disease (CVD) and coronary heart disease (CHD) remains a subject of debate.

Objectives

The objective of this study was to investigate these associations in a population with a high prevalence of dyslipidemia and CVD.

Methods

In a nested case-control study, HDL-C and its subclasses (HDL2-C and HDL3-C) in 370 age and gender-matched case and control subjects were determined. This study employed multivariable-adjusted conditional logistic regression to calculate the odds ratios (ORs) for the associations between HDL-C, HDL2-C, HDL3-C, and HDL2-C/HDL3-C (both as continuous and categorical variables) with incident CVD and CHD. The present study models were adjusted for a comprehensive set of confounders, including body mass index, current smoking, hypertension, type 2 diabetes mellitus, use of lipid-lowering drugs, family history of premature CVD, non-HDL-C, and triglycerides.

Results

In multivariate analysis, when considering lipoprotein parameters as continuous variables, a 1-unit increase in HDL-C and HDL3-C was associated with a reduced risk of incident CVD and CHD. For CVD, the ORs (95% confidence intervals [CI]) were 0.95 (0.92 - 0.98) and 0.95 (0.93 - 0.98) for HDL-C and HDL3-C, respectively. The corresponding values for CHD were 0.94 (0.91 - 0.97) and 0.94 (0.91 - 0.97). In the categorical approach to lipoprotein parameters, higher quartiles of HDL-C and HDL3-C, compared to the first quartile, were significantly associated with a lower risk of incident CVD and CHD. The ORs (95% CI) for the fourth quartiles were 0.43 (0.25 - 0.74, P for trend = 0.003) and 0.46 (0.27 - 0.78, P for trend = 0.005) for HDL-C and HDL3-C regarding CVD and 0.32 (0.17 - 0.59) and 0.32 (0.18 - 0.59) (all P for trend = 0.001) regarding CHD, respectively. Paradoxically, across quartiles of HDL2-C/HDL3-C, this lipid ratio was associated with a higher risk of CHD (92% higher risk in the fourth quartile).

Conclusions

The results showed that HDL3-C, but not HDL2-C, was primarily responsible for the protective effect of HDL-C against CVD, particularly CHD, in Iranian adults.

Supplementation of diet with Brazil nut modulates body composition, bone parameters, and lipid peroxidation in Wistar rats

Oxidative stress, adipose tissue, and bone compartments can be disturbed in chronic diseases. Non-pharmacological strategies, such as Brazil nuts (BNs), can improve these parameters. This study evaluated the effects of BN supplementation at different concentrations on body composition, lipid profile, and peroxidation in healthy rats. Male Wistar rats were divided into three groups: control (CT), Brazil nut 5% (BN5), and Brazil nut 10% (BN10) groups. Body composition, brown adipose tissue (BAT), plasma lipid peroxidation, and lipid profile were evaluated in the three groups. The BN5 group showed an improvement in all bone parameters compared with that of the CT group (p  < .0001). The BN5 and BN10 groups showed reduced plasma lipid peroxidation compared with that of the CT group (p = .0009), whereas the BN10 group presented lower BAT lipid peroxidation than that of the other groups (p = .01). High-density lipoprotein-cholesterol (HDL-c) levels were higher in the BN5 group than in the CT group (p = .01). Conclusively, the use of BNs in a controlled manner promoted improvement in bone parameters, HDL-c levels, and lipid peroxidation in healthy rats. PRACTICAL APPLICATIONS: Nuts has been included in the diet because of their versatility, acceptance, and easy access. Among them, Brazil nut (BN) is considered one of the major known food sources of selenium as well as a source of fibers, unsaturated fatty acids, and phenolic compounds. Studies have shown that BN supplementation is effective in reducing oxidative stress, inflammation, lipid peroxidation, and selenium deficiency when used as a non-pharmacological strategy in experimental models of chronic diseases and in clinical trials. The present study showed that controlled administration of BN improved bone parameters, high-density lipoprotein-cholesterol levels, and lipid peroxidation in healthy rats. Therefore, BN is a promising non-pharmacological agent for the prevention of the onset of chronic non-communicable diseases.

The trend of 10-year cardiovascular risk among diabetic and non-diabetic participants in Tehran Lipid and glucose study: 1999-2018

BACKGROUND

Assessing the risk of cardiovascular disease (CVD) is crucial in preventive cardiology. We aimed to determine the trend of CVD risk among individuals with and without diabetes during two decades of follow-up in a Middle Eastern cohort.

METHODS

We studied 8,450 individuals (55.5% women) aged 40-75 years who participated in the Tehran Lipid and Glucose Study (TLGS). Diabetes status and CVD risk factors were evaluated in six examinations from 1999 to 2018. The individual 10-year CVD risk score was calculated using the ACC/AHA recommended risk equation. We used generalized estimating equation models (GEE) to assess the time trends of CVD risk factors and CVD risk scores in diabetic and non-diabetic groups separately.

RESULTS

The age-adjusted ACC/AHA risk score significantly decreased in non-diabetic women and men (from 3.2% to 1.6% in women and 6.8% to 5.0% in men; p for trend < 0.001). Whereas the risk significantly decreased among diabetics men (from 13.8% to 11.5%), it increased somehow among diabetics women (from 5.3% to 5.5%). Furthermore, in both sexes, diabetic individuals compared to non-diabetic ones had better control on their systolic blood pressure, total cholesterol, and fasting plasma glucose during the last two decades.

CONCLUSIONS

The CVD risk and most CVD risk factors improved in individuals with and without diabetes in the past two decades; however, they have not reached the targets yet. So, more stringent lifestyle modifications and treatment strategies are needed, especially for primary prevention in the general population.

The role of different lipid measures for incident hypertension during more than 12-year follow-up: Tehran Lipid and Glucose Study

The associations of different lipid measures and related indices with incident hypertension during a median follow-up of 12·89 years were examined. Fasting levels of total cholesterol (TC), TAG, HDL-cholesterol and LDL-cholesterol, and related indices (TC/HDL-cholesterol and TAG/HDL-cholesterol) were determined in 7335 Iranian adults (men = 3270) free of hypertension, aged 39·0 (sd 13·2) years. Multivariate Cox proportional hazard regression was applied and lipid parameters were considered either as categorical or continuous variables. During follow-up, 2413 (men = 1126) participants experienced hypertension. Using the first quartile as reference, significant trends were found between quartiles of TAG, HDL-cholesterol, TC/HDL-cholesterol and TAG/HDL-cholesterol in multivariate models; moreover considering these measures as continuous variables, a 1 sd increase in each of these parameters was significantly associated with the risk of incident hypertension; the corresponding hazard ratios and CI were 1·06 (95 % CI 1·02, 1·10), 0·94 (95 % CI 0·89, 0·98), 1·04 (95 % CI 1·01, 1·09) and 1·04 (95 % CI 1·01, 1·07), respectively. The associations between lipid measures and incident hypertension did not change after excluding lipid lowering drug users and those with type 2 diabetes mellitus and these associations were independent of the categories of baseline blood pressure (P for interaction > 0·08). These findings indicate that TAG, TAG/HDL-cholesterol and TC/HDL-cholesterol were independently associated with higher risk, while HDL-cholesterol was associated with lower risk of incident hypertension.

Trends in Serum Lipid Profiles Among Korean Adolescents, 2007-2018

PURPOSE

An adverse lipid profile in adolescence often persists into adulthood, resulting in cardiovascular disease. We aimed to investigate the trends in the prevalence of adverse lipid profiles among Korean adolescents from 2007 to 2018.

PATIENTS AND METHODS

The data were obtained from 9044 adolescents aged 10-19 years who participated in the Korean National Health and Nutrition Examination Surveys (KNHANES) from 2007 to 2018. Fasting serum total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglyceride (TG) levels were analyzed.

RESULTS

Significantly increasing trends in age-standardized prevalence of hypercholesterolemia [from 5.6% to 9.4% in boys (P = 0.004); from 8.1% to 12.4% in girls (P = 0.01)] and hyper-LDL-cholesterolemia [from 4.3% to 8.0% in boys (P = 0.003); from 6.6% to 9.7% in girls (P = 0.035)] were noted in both sexes. In contrast, the prevalence of hypo-HDL-cholesterolemia decreased significantly from 20.0% to 12.5% in boys (<0.001) and from 12.4% to 6.9% in girls (P < 0.001). There were no significant changes in the prevalence of hypertriglyceridemia and hyper-non-HDL-cholesterolemia in both sexes. Accordingly, the overall prevalence of dyslipidemia showed only a modest decline in boys (from 31.8% to 28.7%) and a stable trend in girls (from 28.9% to 28.2%).

CONCLUSION

The prevalence of hypercholesterolemia and hyper-LDL-cholesterolemia increased and that of hypo-HDL-cholesterolemia decreased among Korean adolescents over the recent 12 years. Further studies are needed to explain these trends and possible associations with lifestyle factors.

Non-communicable diseases' risk factors in Iran; a review of the present status and action plans

Non-communicable Diseases (NCDs) are the leading causes of death globally, imposing a heavy burden on the healthcare systems, especially in low- and middle-income countries. Iran is a country in the Middle-East region with an aging population and changing disease risk factors, and now is facing NCDs as the major health problem of the country. Investigating NCDs' risk factors and tackling preventable ones is the main intervention to control their heavy burden. In this review, we discussed the most critical risk factors in Iran and the implemented programs and action plans to control them. A better knowledge on current status of risk factors and plans to tackle them, could help policymakers effectively rule policies and allocate resources to curb heavy burden of NCDs in Iran.

Oxidized Low-Density Lipoprotein Promotes In Vitro Calcification

Calcification plays an important role in the human body in maintaining homeostasis. In the human body, the presence of a high amount of oxidized low-density lipoprotein (ox-LDL) is a consistent feature of the local areas that are common sites of ectopic calcification, namely dental calculus, renal calculus, and the areas affected by arteriosclerosis. Hence, ox-LDL may have some effect on calcification. Scanning electron microscopy (SEM) observation revealed a high amount of amorphous calcium phosphate (ACP) when ox-LDL was included in the solution. In the in vitro experiment, the highest amount of precipitation of calcium phosphate was observed in the solution containing ox-LDL compared to the inclusion of other biomaterials and was 4.2 times higher than that of deionized water for 4.86 mM calcium and 2.71 mM phosphate. The morphology of calcium phosphate precipitates in the solution containing ox-LDL differed from that of the precipitates in solutions containing other biomaterials, as determined by transmission electron microscopy (TEM). Through the time course observation of the sediments using TEM, it was observed that the sediments changed from spherical or oval shape to a thin film shape. These results indicate that sediments acquired a long-range order array, and the phase transitioned from non-crystalline to crystalline with an increased time and density of ACP. Thus, it is concluded that ox-LDL promoted ACP precipitation and it plays an important role in ectopic calcification.

The probiotic Lactobacillus fermentum 296 attenuates cardiometabolic disorders in high fat diet-treated rats

BACKGROUND AND AIM

High-fat (HF) diet consumption has been associated with gut dysbiosis and increased risk of dyslipidemia, type 2 diabetes mellitus and hypertension. Probiotic administration has been suggested as a safe therapeutic strategy for the treatment of cardiometabolic disorders. This study was designed to assess the effects of probiotic Lactobacillus (L.) fermentum 296, a fruit-derived bacteria strain, against cardiometabolic disorders induced by HF diet.

METHODS AND RESULTS

Male Wistar rats were divided into control diet (CTL); HF diet; and HF diet treated with Lactobacillus fermentum 296 (HF + Lf 296). The L. fermentum 296 strain at 1 × 10⁹ colony forming units (CFU)/ml were daily administered by oral gavage for 4 weeks. The results showed that rats fed with HF diet displayed insulin resistance, reduced Lactobacillus spp. counts in feces, serum lipids, and oxidative profile. Rats fed on HF diet also demonstrated augmented blood pressure associated with sympathetic hyperactivity and impaired baroreflex control. The administration of L. fermentum 296 for 4 weeks recovered fecal Lactobacillus sp. counts and alleviated hyperlipidemia, sympathetic hyperactivity, and reduced systolic blood pressure in HF rats without affecting baroreflex sensibility.

CONCLUSION

Our results suggest the ability of L. fermentum 296 improve biochemical and cardiovascular parameters altered in cardiometabolic disorders.

Contributions and Implications of the Tehran Lipid and Glucose Study

Tehran Lipid and Glucose Study (TLGS), an epidemiological study of non-communicable disease with 20 years follow up in a developing country in nutrition transition is a unique study in 15000 family based individuals, 3 - 75 years of age in a part of large city of Tehran. The success rate of recruitment for 20 years, intervention for lifestyle change, and thyroid, reproduction and cardiometabolic genetic studies derived from TLGS have paved suitable path towards precision medicine. In this review, baseline findings and changes of risk factors for the development of NCD including body weight, nutrition, physical activity, blood pressure, tobacco smoking, serum glucose and serum lipids as well as metabolic syndrome, chronic kidney disease, quality of life and biochemical findings in TLGS cohort have been summarized. The results of community based intervention for lifestyle change caused decreases in the prevalence of metabolic syndrome and the incidence of diabetes. It is concluded that TLGS has served as a model for other cohort studies in Iran and the region; it has helped to mobilize scientists in developing countries; it has established locally needed definitions of NCD variables; has served as a model for cohort studies in developing countries in nutrition transition with all socioeconomic constraints and has helped manpower education and development of local CVD risk scores for implementation of NCD management.