The relationship between serum levels of insulin and sex hormone-binding globulin in men: the effect of weight loss

Dietary glycemic index, glycemic load and cancer risk: a meta-analysis of prospective cohort studies

PURPOSE

There is considerable inconsistency in results regarding the association of dietary glycemic index (GI) and glycemic load (GL) with cancer risk. We therefore conducted this systematic review and dose-response meta-analysis of prospective cohort studies to evaluate the relationship between dietary GI/GL and cancer risk.

METHODS

We searched PubMed and Web of Science for prospective cohort studies of dietary GI/GL in relation to risks of all types of cancer up to 31 March 2021. We used a random-effect model to calculate summary relative risks (RR) and 95% confidence intervals (CI). The certainty of evidence was assessed by the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach. This study was registered at PROSPERO (CRD42020215338).

RESULTS

Overall, 55 cohorts were included in the meta-analysis. We assessed the relationship between dietary GI or GL and risks of 23 cancer types, including hormone-related cancers, cancers from digestive system, respiratory system, urinary system and other cancer sites. High GI diet increased overall risk of cancer with low certainty of evidence (highest vs lowest categories, n = 3, RR 1.04, 95% CI 1.01-1.07). For site-specific cancers, high GI diet increased risks of lung cancer (highest vs lowest categories, n = 5, RR 1.08, 95% CI 1.01-1.18) and breast cancer (highest vs lowest categories, n = 14, RR 1.05, 95% CI 1.01-1.09), especially for postmenopausal breast cancer (highest vs lowest categories, n = 10, RR 1.06, 95% CI 1.00-1.13), all with low certainty of evidence. Additionally, dietary GI was positively related to risk of bladder cancer with low certainty of evidence (highest vs lowest categories, n = 3, RR 1.23, 95% CI 1.09-1.40), as well as negatively related to ovarian cancer risk with very low certainty of evidence (highest vs lowest categories, n = 4, RR 0.83, 95% CI 0.69-1.00) and lymphoma risk with low certainty of evidence (highest vs lowest categories, n = 2, RR 0.84, 95% CI 0.72-0.98). Besides, we found an inverse association of dietary GL with lung cancer risk with low certainty of evidence (highest vs lowest categories, n = 5, RR 0.87, 95% CI 0.80-0.94).

CONCLUSION

High dietary GI increased overall cancer risk with low certainty of evidence. For site-specific cancers, high GI diet increased the risks of breast cancer with low certainty of evidence and lung cancer with low certainty of evidence. Dietary GL was inversely associated with lung cancer risk with low certainty of evidence.

Association between preoperative serum insulin levels and lymph node metastasis in endometrial cancer-a prospective cohort study

Endometrial cancer is a common gynecological malignancy in developed countries. Insulin has been identified as a risk factor for endometrial cancer. However, whether insulin levels are related to the risk of lymph node metastasis (LNM) in endometrial cancer is unknown. We conducted a prospective cohort study in a regional hospital to examine the relationships between insulin levels and risk of LNM in premenopausal and postmenopausal women. A total of 668 patients were recruited. Of these, 206 were premenopausal (mean age: 42.01 ± 10.17) and 462 were postmenopausal (mean age: 62.13 ± 13.85). The incidence of LNM in both premenopausal and postmenopausal groups was comparable at 7% and 8%, respectively. In premenopausal women, multivariate logistic regression demonstrated that insulin levels (OR: 2.11, 95% CI: 1.48–2.85, P < 0.05) were significant predictors of LNM risk. In the same group, insulin levels remained significant predictors of LNM risk (cut‐off: 10.48 μIU/mL) when adjusted for body mass index (BMI) (OR: 3.51, 95% CI: 1.42–5.98; P < 0.05) or for waist‐to‐hip ratio (WHR) (OR: 1.87, 95% CI: 1.08–2.66; P < 0.05). Similarly, in postmenopausal women, multivariate logistic regression showed that insulin levels (OR: 1.99, 95% CI: 1.30–2.89; P < 0.05) also significantly predicted LNM risk. This relationship was maintained even after adjustment for BMI (cut‐off: 7.40 μIU/mL, OR: 1.99, 95% CI: 1.01–3.12, P < 0.05) or for WHR (cut‐off: 10.15 μIU/mL, OR: 1.61, 95% CI: 1.04–2.35; P < 0.05). Insulin levels are significantly associated with LNM risk in both premenopausal and postmenopausal women with endometrial cancer. Further prospective studies are needed to examine a potential causal relationship and determine whether its use can offer incremental value for risk stratification in this patient population.

Metabolic syndrome in relation to risk of meningioma

BACKGROUND

Meningioma is a frequent primary intracranial tumor, the etiology of which is potentially related to adiposity. Metabolic syndrome (MetS) is an increasingly common disease characterized by having at least three of the following conditions: central adiposity, arterial hypertension, dyslipidemia, and insulin resistance. Only one prior study investigated MetS in relation to meningioma risk and found a positive association between the two.

RESULTS

Among 2,027 cases and 20,269 controls, body mass index was positively associated with meningioma (p-value for trend < 0.0001). Arterial hypertension was also associated with an increased risk of meningioma (OR = 1.34; 95% CI = 1.20- 1.49). By comparison, high-density lipoprotein, triglycerides, fasting serum glucose, and use of ACE-inhibitors, AT-II inhibitors, beta-blockers, diuretics, calcium antagonists, nitrates, or statins were not associated with risk of meningioma.

MATERIALS AND METHODS

We conducted a matched case-control analysis using data from the U.K.-based Clinical Practice Research Datalink (CPRD) to analyse medical conditions and treatments related to MetS in cases with meningioma and meningioma-free controls. We identified all cases with an incident diagnosis of meningioma between 1995 and 2015 and matched each to ten controls on age, sex, calendar time, general practice, and number of years of active history in the CPRD prior to the index date. Exposures were assessed using computerised records. We conducted conditional logistic regression analysis to determine relative risks, estimated as odds ratios (ORs) with 95% confidence intervals (CIs), adjusted for confounding factors.

CONCLUSIONS

Obesity and arterial hypertension are positively associated with risk of meningioma. Further studies are needed to better understand potential underlying biologic mechanisms.

Obesity and Cancer: An Angiogenic and Inflammatory Link

With the current epidemic of obesity, a large number of patients diagnosed with cancer are overweight or obese. Importantly, this excess body weight is associated with tumor progression and poor prognosis. The mechanisms for this worse outcome, however, remain poorly understood. We review here the epidemiological evidence for the association between obesity and cancer, and discuss potential mechanisms focusing on angiogenesis and inflammation. In particular, we will discuss how the dysfunctional angiogenesis and inflammation occurring in adipose tissue in obesity may promote tumor progression, resistance to chemotherapy, and targeted therapies such as anti-angiogenic and immune therapies. Better understanding of how obesity fuels tumor progression and therapy resistance is essential to improve the current standard of care and the clinical outcome of cancer patients. To this end, we will discuss how an anti-diabetic drug such as metformin can overcome these adverse effects of obesity on the progression and treatment resistance of tumors.

Clinical management of infertile men with nonobstructive azoospermia

The clinical management of men with nonobstructive azoospermia (NOA) seeking fertility has been a challenge for andrologists, urologists, and reproductive medicine specialists alike. This review presents a personal perspective on the clinical management of NOA, including the lessons learned over 15 years dealing with this male infertility condition. A five-consecutive-step algorithm is proposed to manage such patients. First, a differential diagnosis of azoospermia is made to confirm/establish that NOA is due to spermatogenic failure. Second, genetic testing is carried out not only to detect the males in whom NOA is caused by microdeletions of the long arm of the Y chromosome, but also to counsel the affected patients about their chances of having success in sperm retrieval. Third, it is determined whether any intervention prior to a surgical retrieval attempt may be used to increase sperm production. Fourth, the most effective and efficient retrieval method is selected to search for testicular sperm. Lastly, state-of-art laboratory techniques are applied in the handling of retrieved gametes and cultivating the embryos resulting from sperm injections. A coordinated multidisciplinary effort is key to offer the best possible chance of achieving a biological offspring to males with NOA.

Serum insulin, glucose, indices of insulin resistance, and risk of prostate cancer

BACKGROUND

The mitogenic and growth-stimulatory effects of insulin-like growth factors appear to play a role in prostate carcinogenesis, yet any direct association of circulating insulin levels and risk of prostate cancer remains unclear.

METHODS

We investigated the relationship of the level of serum insulin, glucose, and surrogate indices of insulin resistance (ie, the molar ratio of insulin to glucose and the homeostasis model assessment of insulin resistance [HOMA-IR]) to the development of prostate cancer in a case-cohort study within the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study cohort of Finnish men. We studied 100 case subjects with incident prostate cancer and 400 noncase subjects without prostate cancer from the larger cohort. Fasting serum was collected 5-12 years before diagnosis. We determined insulin concentrations with a double-antibody immunochemiluminometric assay and glucose concentrations with a hexokinase assay. Multivariable logistic regression models estimated relative risks as odds ratios (ORs), and all statistical tests were two-sided.

RESULTS

Insulin concentrations in fasting serum that was collected on average 9.2 years before diagnosis among case subjects were 8% higher than among noncase subjects, and the molar ratio of insulin to glucose and HOMA-IR were 10% and 6% higher, respectively, but these differences were not statistically significant. Among subjects in the second through fourth insulin quartiles, compared with those in the first quartile, increased insulin levels were associated with statistically significantly increased risks of prostate cancer (OR = 1.50, 95% confidence interval [CI] = 0.75 to 3.03; OR = 1.75, 95% CI = 0.86 to 3.56; and OR = 2.55, 95% CI = 1.18 to 5.51; for the second through fourth insulin quartiles, respectively; P(trend) = .02). A similar pattern was observed with the HOMA-IR (OR = 2.10, 95% CI = 1.03 to 4.26; P(trend) = .02) for the highest vs lowest quartiles. Risk varied inconsistently with glucose concentration (P(trend) = .38). A stronger association between insulin level and prostate cancer risk was observed among leaner men and among men who were less physically active at work. Crude prostate cancer incidence was 154 prostate cancers per 100 000 person-years in the lowest quartile of fasting serum insulin vs 394 prostate cancers per 100 000 person-years in the highest quartile.

CONCLUSION

Elevated fasting levels of serum insulin (but not glucose) within the normal range appear to be associated with a higher risk of prostate cancer.

Polymorphism of the insulin gene is associated with increased prostate cancer risk

High insulin levels are linked with increased cancer risk, including prostate cancer. We examined the associations between prostate cancer with polymorphisms of the insulin gene (INS) and its neighbouring genes, tyrosine-hydroxylase and IGF-II (TH and IGF2). In this study, 126 case-control pairs matched on age, race, and countries of origin were genotyped for +1127 INS-PstI in INS, -4217 TH-PstI in TH, and +3580 IGF2-MspI in IGF2. The homozygous CC genotype of +1127 INS-PstI occurred in over 60% of the population. It was associated with an increased risk of prostate cancer in nondiabetic Blacks and Caucasians (OR=3.14, P=0.008). The CC genotype was also associated with a low Gleason score <7 (OR=2.60, P=0.022) and a late age of diagnosis (OR=2.10, P=0.046). Markers in the neighbouring genes of INS showed only null to modest associations with prostate cancer. The polymorphism of INS may play a role in the aetiology of prostate cancer. Given the high prevalence of the CC genotype and its association with late age of onset of low-grade tumours, this polymorphism may contribute to the unique characteristics of prostate cancer, namely a high prevalence of indolent cancers and the dramatic increase in incidence with age.