COMMENTARIES

Metabolic Abnormalities and Prostate Pathologies: the Sub-Saharan African Experience

Chukwunonso E.C.C. Ejike, Clinical Nutrition and Chronic Diseases Unit, Department of Biochemistry, Michael Okpara University of Agriculture, Umudike, PMB 7267 Umuahia, Nigeria
Please address correspondence to:
Chukwunonso E.C.C. Ejike
Clinical Nutrition and Chronic Diseases Unit
Department of Biochemistry
Michael Okpara University of Agriculture
Umudike, PMB 7267 Umuahia, Nigeria
Mobile phone: +2348036066777
Email: nonsoejikeecc@yahoo.com

Introduction

Urbanization is taking place at different rates in different parts of sub-Saharan Africa. This has resulted in a change in the nature of jobs undertaken, foods eaten, and available machines/energy-sparing devices in the region. It has also resulted in a change in the disease pattern of the region, with chronic diseases now competing with communicable diseases for the often meager health budgets of the countries in the region. This commentary discusses the diseases associated with this urbanization-driven change in lifestyle – metabolic abnormalities –, their rising prevalence with urbanization, and their relationship with benign prostate hyperplasia (BPH) and prostate cancer (PC).

 

Benign Prostate Hyperplasia (BPH) and Prostate Cancer (PC)

The prostate is hormone sensitive and androgens (and to some extent estrogens) are known to be involved in the normal and aberrant growth of prostatic cells. In men, PC is the most common non-cutaneous cancer [1]. The incidence rate for PC in African Americans (275.3 per 100,000) is about 60% higher than that for whites (172.9 per 100,000) [2,3]. Documented prevalence data on PC in sub-Saharan Africa is rather scanty or unavailable. BPH is a neoplastic condition of the prostate gland that clinically presents as bladder outlet obstructions and lower urinary tract symptoms (LUTS) [4]. In Nigeria, the prevalence of BPH is as high as 25.35% [5] as against 10.6% in South Korea [6]. In terms of etiology, BPH and PC are closely related, differing largely in the fact that a carcinogen is required to initiate cancerous growth.

 

Diet as a Risk Factor for both Metabolic Abnormalities and Prostate Diseases

As a result of urbanization, the foods eaten by sub-Saharan African countries (especially in urban centers) now resemble those of Western countries. The price is however the attendant epidemiologic change observed in the region. The abundance of food and its over-consumption results in imbalances in energy intake and expenditure and can be explained by the “thrifty genotype” hypothesis. The hypothesis postulates that for selective survival advantage in times of fluctuating plenty and famine (which is the case in the wild), animals developed a highly efficient storage mechanism for calories in times of plenty to be used in times of famine [7]. This “thrifty genotype” however becomes a problem in times of regular abundance (as is epitomized by urbanization and the wealth it brings) and leads to the metabolic abnormalities under discussion.

          It has been suggested that dietary fat alters androgen and insulin-like growth factor levels and produces free radicals, all of which are linked to PC and BPH [8]. A high animal fat or low fiber diet may affect the development of PC (and BPH) at all levels of human development – in utero, childhood and adulthood – by affecting the “gonadostat set point,” thereby inducing early puberty or increasing circulating testosterone levels – processes that lead to a high expression of 5α reductase [the enzyme that converts testosterone to the more potent androgen – dihydrotestosterone (DHT)]. This leads to an increase in intracellular DHT, thereby triggering rapid cellular proliferation and resulting in BPH or PC [9].

 

Metabolic Abnormalities: Prevalence in sub-Saharan Africa, and Relationship with PC and BPH

Insulin resistance, central adiposity/obesity, impaired fasting glucose, low levels of high-density lipoprotein cholesterol, elevated triglycerides, and hypertension are the major metabolic abnormalities that result from the change that often comes with urbanization.

          Insulin resistance describes a condition of impaired biological response to the action of insulin [10]. This results in an increase in insulin release, which if sustained, leads to hyperinsulinemia [11]. Hyperinsulinemia halts the action of hormone-sensitive lipase, thereby causing fats to remain within fat stores, otherwise called adipocytes [12]. The lack of mobilization of stored fat leads to obesity/adiposity and then to deregulation and/or over-expression of the IGF system, which has been implicated in the etiology of BPH and PC [13,14]. Abdominal obesity has been shown to be linked to the development of BPH and PC [15-18].

          Impaired glucose metabolism results in diabetes mellitus. In sub-Saharan Africa, the prevalence of diabetes is 1% in rural areas, but up to 7% an 13% in urban areas and the more developed cities, respectively [19,20]. Research has shown that men with fast growing BPH have a higher prevalence of non-insulin dependent diabetes mellitus (NIDDM) [21]. NIDDM is often associated with a cluster of lipid abnormalities known as hypercholesterolemia. The prevalence of hypercholesterolemia is as low as 0.1% in rural Gambia, but as high as 16.5% in urban South Africa [22,23]. It is suggested that hypercholesterolemia alters prostate morphology by affecting the sex steroid axis, and that way affects BPH and PC pathogenesis [24].

          Visceral obesity is a major risk factor for hypertension, defined as a sustained systolic blood pressure of 140 mmHg or more and a sustained diastolic blood pressure of 90 mmHg or more [25]. The prevalence of hypertension is highest in urban sub-Saharan Africa and lowest in the rural areas [26,27]. Again, hypertension has been shown to be a risk factor for BPH [21].

 

Conclusion

The prevalence of both metabolic abnormalities, on the one hand, and that of prostate disorders, on the other hand, is high and often positively correlated, in the developed countries. It is unlikely that this is not the case in sub-Saharan Africa. The prevalence of these metabolic abnormalities in sub-Saharan Africa has been shown to increase with increasing urbanization, hence their near-absence in the rural areas, and appreciable presence in the urban areas. However, little is documented on the prevalence of BPH and PC in the region, leading to a possible erroneous feeling that their prevalence is negligible. The short life-span of men in sub-Saharan Africa and the poor level of screening and reportage of cases may mask the rising prevalence of BPH and PC especially in urban sub-Saharan Africa [28].

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