Diabetes mellitus and female sexual response: what do animal models tell us?

BACKGROUND

One of the less explored effects of diabetes mellitus (DM) is female sexual dysfunction. Females of different species have been used as models.

AIM

To analyze the information of animal models of DM and female sexual response (FSR).

METHODS

The literature of FSR in models of DM was reviewed.

OUTCOMES

Paradigm- and diabetes-dependent changes have been found in various aspects of the FSR.

RESULTS

Females in a type 1 DM (DM1) model show a decrease in the number of proestrus events, and ovariectomized females treated with sex hormones have been used. In these females, a reduction in lordosis has been reported; in proceptivity, the data are contradictory. These females present a decrease in sexual motivation that was restored after exogenous insulin. In the type 2 DM (DM2) model, females show regular estrous cycles, normal levels of lordosis behavior, and, depending on the paradigm, decreased proceptivity. These females display normal preference for sexually active males or their olfactory cues when having free physical contact; they lose this preference when tested in paradigms where physical interaction is precluded.

CLINICAL TRANSLATION

Preclinical data showing the high deleterious effects of a DM1 model and the less drastic effects under a DM2 model are in accordance with clinical data revealing a much higher prevalence of sexual dysfunction in women with DM1 than DM2.

STRENGTHS AND LIMITATIONS

The main strength is the analysis of the changes in various components of FSR in 2 models of DM. The main limitation is the difficulty in extrapolating the data on FSR from rats to women and that most studies focus on evaluating the impact of severe or chronic-moderate hyperglycemia/hyperinsulinemia on the sexual response, without considering other pathophysiologic alterations generated by DM.

CONCLUSION

Females with severe hyperglycemia have a decrease in FSR, while those with moderate hyperglycemia show much less drastic effects.

Reduced sexual motivation of diabetic female rats: Restoration with insulin

The aim of this study was to evaluate female rat sexual motivation in a model of diabetes mellitus type 1. Severe hyperglycemia was induced in ovariectomized Wistar rats by injecting streptozotocin [STZ, 100 mg/kg, i.p.]. Ten days later, females received estradiol benzoate (10 μg/rat, s.c.) plus progesterone (3 mg/rat, s.c.). A group of STZ-treated animals was administered with insulin (2-4 U) every 12 h for 10 days, which normalized glucose levels. In the partner preference (PP) and sexual incentive motivation (SIM) tests, control females spent more time close to a sexually experienced male (SE) than with a castrated male (CM). STZ-treated females stayed the same amount of time with both stimuli, that is, they lost their sexual preference. We also evaluated the sense of smell using two behavioral tests, one related to sexual odors (SO) and another one to food odors (FO). In the SO test, control females spent more time sniffing the sawdust coming from cages that contained SE males; hyperglycemic females remained the same amount of time sniffing the sawdust of both stimuli: SE and CM. In the FO test, no differences were found between control and STZ-treated groups. Insulin treatment reverted the changes observed in hyperglycemic females in the PP, SIM and SO tests. These data suggest that severe hyperglycemia decreases sexual motivation and that insulin recovers such diminution.

Does Chronic Hyperglycemia Affect Female Rat Sexual Behavior? Differences in Paced and Non-Paced Mating

INTRODUCTION

Diabetes mellitus has been associated with sexual dysfunction; however, in women this relationship is controversial. A study using a model of type 2 diabetes mellitus (DM2) failed to find a reduced receptivity in the non-paced mating (NPM), but the appetitive aspects of female sexual behavior have not been evaluated, for example, in the paced mating (PM) paradigm.

AIM

To evaluate all components of female sexual behavior (in NPM and PM) in a model of DM2 using ovariectomized (OVX) (treated with steroids) or intact female rats (non-OVX) in natural proestrus.

METHODS

Neonatal females (3-4 days) were administered streptozotocin (STZ, 70 mg/kg, intraperitoneally) or citrate buffer. At week 8, a glucose tolerance test was performed. At week 10, half of the females were OVX, and in the other half (non-OVX) the estrous cycle was monitored. At the twelfth week, the sexual behavior tests were conducted; OVX females were treated with estradiol benzoate (10 μg, -24 hours) and progesterone (3 mg, -4 hours), whereas the non-OVX were evaluated on vaginal proestrus.

MAIN OUTCOME MEASURES

We registered in NPM and PM receptivity (lordosis quotient and intensity), as well as the number of proceptive and aggressive behaviors. Additionally, in PM we calculated the percentage of exits and the return latencies after receiving stimulation and the time the female remained in the male's compartment.

RESULTS

The STZ-treated females presented glucose intolerance and were hyperglycemic. Neonatal STZ treatment provoked changes in the females' sexual behavior depending on the paradigm and the hormonal condition. In the NPM, STZ-OVX females had decreased lordosis quotient and intensity and increased aggression, whereas, in the STZ-non-OVX females, there was a decrease in proceptivity; such changes were not observed in PM. Regardless of whether the STZ-treated females were OVX, they failed to perform the pacing behavior.

CLINICAL IMPLICATION

These data support the idea that chronic mild hyperglycemia, like that observed in DM2 (which represents 90% of the clinical cases), provokes marginal changes in most aspects of female sexual behavior.

STRENGTHS & LIMITATIONS

The main strength of this work is the evaluation of consummatory and motivational aspects of female sexual behavior in a model of DM2. The main limitation is the duration of the experimental design that does not resemble the course of the disease in humans. No histologic or biochemical analyses were performed.

CONCLUSION

These results suggest that chronic hyperglycemia produces decreases in sexual behavior. Hernández-Munive AK, Rebolledo-Solleiro D, Fernández-Guasti A. Does Chronic Hyperglycemia Affect Female Rat Sexual Behavior? Differences in Paced and Non-Paced Mating. J Sex Med 2019;16:1130-1142.