Effect of Berberine on Cardiovascular Disease Risk Factors: A Mechanistic Randomized Controlled Trial

Cardiovascular disease (CVD) is a major contributor to the global burden of disease. Berberine, a long-standing, widely used, traditional Chinese medicine, is thought to have beneficial effects on CVD risk factors and in women with polycystic ovary syndrome. The mechanisms and effects, specifically in men, possibly via testosterone, have not been examined previously. To assess the effect of berberine on CVD risk factors and any potential pathway via testosterone in men, we conducted a randomized, double-blind, placebo-controlled, parallel trial in Hong Kong. In total, 84 eligible Chinese men with hyperlipidemia were randomized to berberine (500 mg orally, twice a day) or placebo for 12 weeks. CVD risk factors (lipids, thromboxane A2, blood pressure, body mass index and waist–hip ratio) and testosterone were assessed at baseline, and 8 and 12 weeks after intervention. We compared changes in CVD risk factors and testosterone after 12 weeks of intervention using analysis of variance, and after 8 and 12 weeks using generalized estimating equations (GEE). Of the 84 men randomized, 80 men completed the trial. Men randomized to berberine had larger reductions in total cholesterol (−0.39 mmol/L, 95% confidence interval (CI) −0.70 to −0.08) and high-density lipoprotein cholesterol (−0.07 mmol/L, 95% CI −0.13 to −0.01) after 12 weeks. Considering changes after 8 and 12 weeks together, berberine lowered total cholesterol and possibly low-density lipoprotein-cholesterol (LDL-c), and possibly increased testosterone. Changes in triglycerides, thromboxane A2, blood pressure, body mass index and waist–hip ratio after the intervention did not differ between the berberine and placebo groups. No serious adverse event was reported. Berberine is a promising treatment for lowering cholesterol. Berberine did not lower testosterone but instead may increase testosterone in men, suggesting sex-specific effects of berberine. Exploring other pathways and assessing sex differences would be worthwhile, with relevance to drug repositioning and healthcare.

The Impact of Testosterone on the QT Interval: A Systematic Review

Humans and mammals have sex-specific differences in cardiac electrophysiology, linked to the action of sex hormones in the cardiac muscle. These hormones can upregulate or downregulate the expression of ionic channels modulating the cardiac cycle through genomic and non-genomic interactions. Systematic search in PubMed, Medline and EMBASE including keywords pertaining to testosterone and QT interval. Included experimental studies and observation studies and case reports presenting the results of testosterone administration, excess or deficiency in humans and animals. Testosterone has been shown to shorten the action potential duration, by enhancing the expression of K⁺ channels and downregulating I_CaL increasing the repolarization reserve of the cardiac muscle. This effect has been observed in both genders and animals. Testosterone deficient states can promote arrhythmogenesis. The evidence in this paper may be used to guide clinical considerations, such as increased clinical surveillance of patients in testosterone deficient states using ECG.

Genetic predictors of testosterone and their associations with cardiovascular disease and risk factors: A Mendelian randomization investigation

Background

Testosterone supplementation has been linked to increased cardiovascular disease risk in some observational studies. The causal role of testosterone can be investigated using a Mendelian randomization approach.

Methods and results

We assessed genetic associations of variants in two gene regions (SHBG and JMJD1C) with several cardiovascular risk factors (lipids, adiponectin, blood pressure, anthropometric traits) plus male pattern baldness, including control outcomes and potential mediators. We assessed genetic associations with coronary artery disease (CAD) risk in the CARDIoGRAMplusC4D consortium (171,191 individuals including 60,801 cases), and associations with CAD and ischaemic stroke risk in the UK Biobank (367,643 individuals including 25,352 CAD cases and 3650 ischaemic stroke cases).

Genetic predictors of increased serum testosterone were associated with lipids, blood pressure, and height. There was some evidence of an association with risk of CAD (SHBG gene region: odds ratio (OR) 0.95 per 1 unit increase in log-transformed testosterone [95% confidence interval: 0.81–1.12, p = 0.55]; JMJD1C gene region: OR 1.24 [1.01–1.51, p = 0.04]) and ischaemic stroke both overall (SHBG: OR 1.05 [0.64, 1.73, p = 0.83]; JMJD1C: OR 2.52 [1.33, 4.77, p = 0.005]) and in men. However, associations with some control outcomes were in the opposite direction to that expected.

Conclusions

Sex hormone-related mechanisms appear to be relevant to cardiovascular risk factors and for stroke (particularly for men). However, the extent that these findings are specifically informative about endogenous testosterone or testosterone supplementation is unclear. These findings underline a fundamental limitation for the use of Mendelian randomization where biological knowledge about the function of genetic variants is uncertain.

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Genetic predictors of testosterone were associated with cardiovascular risk factors, such as lipids and blood pressure.

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However, associations were not consistent between the two gene regions considered in this analysis.

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Some genetic predictors of increased testosterone associated with higher coronary artery disease and ischaemic stroke risk.

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This suggests that some sex hormone-related mechanisms are implicated in cardiovascular disease.

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However, the extent to which these analyses are predictive of the effects of testosterone supplementation is unclear.

Mendelian randomization estimates of alanine aminotransferase with cardiovascular disease: Guangzhou Biobank Cohort study

Observational studies of the association of alanine aminotransferase (ALT) levels with ischaemic heart disease (IHD) and cardiovascular disease (CVD) risk factors are inconsistent, probably because of confounding and reverse causality. Mendelian randomization (MR) provides less confounded results. We used MR analysis to assess the associations of ALT (U/L) with IHD, diabetes and other CVD risk factors. We used instrumental variable analysis based on two single nucleotide polymorphism (SNPs) HSD17B13/MAPK10 (rs6834314) and PNPLA3/SAMM50 (rs738409) to assess the associations of ALT (U/L) with IHD, diabetes and other CVD risk factors in the Guangzhou Biobank Cohort Study (GBCS). Observationally in 19,925 participants ALT levels were strongly positively associated with self-reported IHD, systolic and diastolic blood pressure, low-density lipoprotein- and total cholesterol, triglycerides, fasting glucose, body mass index, waist circumference, heart rate (HR) and diabetes, but were not associated with uncorrected QT interval, HR-corrected QT interval or high-density lipoprotein-cholesterol. In the MR study, using a credible genetic instrument (F-statistic = 23) for ALT, ALT levels were negatively associated with IHD (odds ratio (OR) 0.92, 95% confidence interval (CI) 0.87 to 0.97) and triglycerides (β - 0.08, 95% CI - 0.13 to - 0.03), but were not associated with other CVD risk factors. Our results using Mendelian randomization suggest that ALT reduces the risk of IHD, probably through reducing triglyceride levels. The underlying mechanisms deserve further investigation.

Tachykinin neurokinin 3 receptor antagonists: a new treatment for cardiovascular disease?

Great progress has been made in reducing cardiovascular mortality over the past 50 years. Nevertheless, prevalence is rising in some settings and remains higher in men than in women, even with the same level of established risk factors. To gain new insights, researchers are now considering cardiovascular disease in relation to the well known evolutionary biology model of growth and reproduction trading off against longevity, with trials of calorie restriction underway. However, calorie restriction has not been as successful as expected in primates and it is increasingly realised that effects on the reproductive axis might also be important. In this paper, the modulation of the reproductive axis using existing agents that have such properties-tachykinin neurokinin 3 receptor antagonists-is proposed as a way of reducing cardiovascular disease and combating a leading cause of global morbidity and mortality.

Endogenous androgen exposures and ischemic heart disease, a separate sample Mendelian randomization study

BACKGROUND

Evolutionary biology suggests growth and reproduction trade-off against longevity. Correspondingly estrogen supplementation failed to increase lifespan. Testosterone supplementation is widely used by older men, although regulators have warned of its cardiovascular risk. No large trial of testosterone exists. We examined how genetic determinants of up-regulation (follicle-stimulating hormone (FSH)) and down-regulation (anti-Müllerian hormone (AMH) and testicular dysgenesis syndrome (TDS)) of mainly the male reproductive system are associated with ischemic heart disease (IHD).

METHODS

Separate sample instrumental variable analysis with genetic instruments, i.e., Mendelian randomization, was used to obtain unconfounded estimates using large case-control studies of coronary artery disease/myocardial infarction (CAD/MI) with extensive genotyping, i.e., CARDIoGRAMplusC4D (64,374 CAD/MI cases, 130,681controls), or CARDIoGRAMplusC4D 1000 Genomes (60,801 cases, 123,504 controls).

RESULTS

Genetically predicted FSH was positively associated with CAD/MI (odds ratio (OR) 1.08, 95% confidence interval (CI) 1.03 to 1.13 per mIU/mL FSH). Genetically predicted AMH and TDS were inversely associated with CAD/MI (OR 0.93, 95% CI 0.87 to 0.998 per ng/mL log AMH and OR 0.89, 95% CI 0.81 to 0.98 per log OR higher risk of TDS).

CONCLUSIONS

As expected from evolutionary biology, genetically predicted FSH, related to higher androgens in men and women, was positively associated with IHD, while genetically predicted AMH and TDS, related to lower androgens in men, were inversely associated with IHD. Androgens might be a modifiable causal factor underlying men's greater vulnerability to IHD, with corresponding implications for use of testosterone supplementation as well as for prevention and treatment of IHD.

A Mendelian randomization study of testosterone and cognition in men

Testosterone replacement for older men is increasingly common, with some observations suggesting a protective effect on cognitive function. We examined the association of endogenous testosterone with cognitive function among older men in a Mendelian randomization study using a separate-sample instrumental variable (SSIV) analysis estimator to minimize confounding and reverse causality. A genetic score predicting testosterone was developed in 289 young Chinese men from Hong Kong, based on selected testosterone-related single nucleotide polymorphisms (rs10046, rs1008805 and rs1256031). The association of genetically predicted testosterone with delayed 10-word recall score and Mini-Mental State Examination (MMSE) score was assessed at baseline and follow-up using generalized estimating equation among 4,212 older Chinese men from the Guangzhou Biobank Cohort Study. Predicted testosterone was not associated with delayed 10-word recall score (-0.02 per nmol/L testosterone, 95% confidence interval (CI) -0.06-0.02) or MMSE score (0.06, 95% CI -0.002-0.12). These estimates were similar after additional adjustment for age, education, smoking, use of alcohol, body mass index and the Framingham score. Our findings do not corroborate observed protective effects of testosterone on cognitive function among older men.